System and method for operating a rechargeable electrochemical cell or battery

ABSTRACT

An electrochemical cell management system comprising an electrochemical cell and at least one controller configured to control the cell such that, for at least a portion of a charge cycle, the cell is charged at a charging rate or current that is lower than a discharging rate or current of at least a portion of a previous discharge cycle. An electrochemical cell management method. An electrochemical cell management system comprising an electrochemical cell and at least one controller configured to induce a discharge of the cell before and/or after a charging step of the cell. An electrochemical cell management method. A electrochemical cell management system comprising an electrochemical cell and at least one controller configured to: monitor at least one characteristic of the cell and, based on the at least one characteristic of the cell, induce a discharge and/or control a charging rate or current of the cell.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/670,933 (now U.S. Pat. No. 11,056,728), filed Oct. 31, 2019, andentitled “System and Method for Operating a Rechargeable ElectrochemicalCell or Battery,” which is incorporated herein by reference in itsentirety for all purposes.

TECHNICAL FIELD

Charge/discharge management of electrochemical cells, and relatedsystems, are generally described.

BACKGROUND

Conventionally, batteries have failed to compete successfully withestablished power sources such as combustion engines in variousindustries, such as vehicles. One reason for this failure has been thatbattery users have been dissatisfied with the longevity and performancethat batteries have conventionally provided.

SUMMARY

Disclosed herein are embodiments related to charge/discharge managementof electrochemical cells and related systems. The subject matter of thepresent invention involves, in some cases, interrelated products,alternative solutions to a particular problem, and/or a plurality ofdifferent uses of one or more systems and/or articles.

Some embodiments are directed to an electrochemical cell managementsystem comprising: an electrochemical cell, and at least one controllerconfigured to control the cell such that, for at least a portion of acharge cycle, the cell is charged at a charging rate or current that islower than a discharging rate or current of at least a portion of aprevious discharge cycle.

Some embodiments are directed to an electrochemical cell managementsystem comprising: an electrochemical cell, and at least one controllerconfigured to monitor at least one characteristic of the cell, the atleast one characteristic comprising at least one of: at least a portionof a discharge history of the cell, and at least one morphologicalcharacteristic of the cell, and based on the at least one characteristicof the cell, induce a discharge of the cell and/or control a chargingrate or current of the cell.

Certain embodiments are directed to an electrochemical cell managementsystem comprising: an electrochemical cell, and at least one controllerconfigured to induce a discharge of the cell before and/or after acharging step of the cell.

Further embodiments are directed to an electrochemical cell managementmethod. The method may comprise controlling an electrochemical cell suchthat, for at least a portion of a charge cycle, the cell is charged at acharging rate or current that is lower than a discharging rate orcurrent of at least a portion of a previous discharge cycle.

Additional embodiments are directed to an electrochemical cellmanagement method. The method may comprise inducing a discharge of anelectrochemical cell before and/or after a charging step of the cell.

Some embodiments are directed to an electrochemical cell managementmethod. The method may comprise monitoring at least one characteristicof the cell, the at least one characteristic comprising at least one of:at least a portion of a discharge history of the cell, and at least onemorphological characteristic of the cell; and based on the at least onecharacteristic of the cell, inducing a discharge of the cell and/orcontrolling a charging rate or current of the cell.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1A is a block diagram illustrating a representative electrochemicalcell management system, according to some embodiments.

FIGS. 1B-1D are current-time graphs illustrating representative chargingschemes for a representative electrochemical cell management system,according to some embodiments.

FIG. 1E is a circuit diagram illustrating a representative simplifiedelectrochemical cell model, according to some embodiments.

FIG. 1F is a block diagram illustrating a representative batterymanagement system, according to some embodiments.

FIG. 2 is a block diagram illustrating a representative battery pack,according to some embodiments.

FIG. 3A is a block diagram illustrating a representative batterymanagement system, according to some embodiments.

FIG. 3B is a block diagram illustrating a representative cell set andcorresponding components, according to some embodiments.

FIG. 3C is a cross-sectional schematic diagram illustrating theapplication of an anisotropic force to one or more electrochemicalcells, according to some embodiments.

FIG. 3D is a cross-sectional schematic diagram of electrochemical cells,according to some embodiments.

FIG. 4A is a flow chart depicting a representative process forcontrolling a charging rate or current of a cell, according to someembodiments.

FIG. 4B is a flow chart depicting an additional representative processfor controlling a charging rate or current of a cell, according to someembodiments.

FIG. 4C is a flow chart depicting a representative process for inducingdischarge of a cell, according to some embodiments.

FIG. 4D is a flow chart depicting an additional representative processfor inducing discharge of a cell, according to some embodiments.

FIG. 5A is a flow chart depicting a representative process formonitoring cell characteristic(s) and inducing discharge or controllingthe charge rate or current of the cell, according to some embodiments.

FIG. 5B is a flow chart depicting an additional representative processfor monitoring cell characteristic(s) and inducing discharge orcontrolling the charge rate or current of the cell, according to someembodiments.

FIG. 6A is a flow chart depicting a representative process fordischarging sets of cells of a battery, according to some embodiments.

FIG. 6B is a flow chart depicting an additional representative processfor discharging sets of cells of a battery, according to someembodiments.

FIG. 6C is a flow chart depicting a representative process forcontrolling a battery pack, according to some embodiments.

FIG. 6D is a flow chart depicting an additional representative processcontrolling a battery pack, according to some embodiments.

FIG. 7A is a chart depicting an exemplary discharge profile, accordingto some embodiments.

FIG. 7B is a chart depicting an exemplary full discharge profile,according to some embodiments.

FIG. 7C is a chart depicting an exemplary battery cycle life, accordingto some embodiments.

FIG. 8 is a block diagram depicting a representative computing systemthat may be used to implement certain aspects.

DETAILED DESCRIPTION

The inventors have recognized and appreciated that conventionaltechniques for management and operation of rechargeable electrochemicalcells have resulted in the previously poor longevity and performance ofcells (and batteries in which they may be included). For example, cellshave suffered a short cycle life (e.g., a low number of complete chargeand discharge cycles before capacity falls below 80% of originalcapacity, as cells typically do at some point after sufficient usage),particularly where charge and discharge rates are similar, or where thecharge rate is higher than the discharge rate. For example, many usersof cells in batteries have desired the batteries to have nearlyidentical charge and discharge rates (e.g., 4 hours to charge and 4hours to discharge), and battery manufacturers have provided batteriesand battery management systems that provide such nearly identical rates.Many users have also desired batteries to charge at higher rates thanthey discharge (e.g., 30 minutes to charge and 4 hours to discharge) forvarious reasons, such as to reduce inconvenience of waiting for chargingto use the batteries.

The term “complete charge cycle” is used herein to generally refer to aperiod of time during which about 100% of a cell's re-charge capacity ischarged, and the term “complete discharge cycle” is used to generallyrefer to a period of time during which about 100% of the cell'sdischarge capacity (which may be different from it re-charge capacity)is discharged. On the other hand, the term “charging step” is usedherein to generally refer to a continuous period of time during whichcharging is performed without discharging, and the term “dischargingstep” is used herein to generally refer to a continuous period duringwhich discharging is performed without charging.

The term “charge cycle” is used to generally refer to a period of timeduring which the cell is charged, and it need not be a complete chargecycle. The term “discharge cycle” is used to generally refer to a periodof time during which the cell is discharged, and it need not be acomplete discharge cycle. The term “previous discharge cycle” is used togenerally refer to a period of time during which the cell has been or isbeing discharged. For example, this “previous” discharge cycle may havebeen completed or may still be in progress—it need not refer to the mostrecent completed discharging steps that sum to about 100% of the cell'sdischarge capacity. If no complete discharge cycle has been performed,the previous discharge cycle may refer to any previously completeddischarging steps.

The term “capacity” is used to generally refer to an amount ofelectrical charge a cell or cells can deliver at a given or ratedvoltage and is often measured in amp-hours (such as milliamp-hours ormAh). In some embodiments, capacity may be the mAh a cell or cells canhold at a given point in time (which may change over multiple charge ordischarge cycles), it may be the mAh remaining in a cell or cells at agiven point in time, or it may be the mAh a cell or cells need to fullyre-charge.

The inventors have recognized and appreciated that the cycle life of acell (and a battery including the cell), and consequently the longevityand performance of the cell (and battery), may be greatly improved byemploying higher ratios of discharge rate to charge rate. Furthermore,the inventors have recognized and appreciated that these ratios may beemployed by providing a cell and/or battery management system thatcontrols the cell or cells to provide such ratios.

For example, some embodiments are directed to a cell management systemthat controls a cell such that, for at least a portion of a chargecycle, the cell is charged at a charging rate or current that is lowerthan a discharging rate or current of at least a portion of a previousdischarge cycle. As another example, some embodiments are directed to acell management system that monitors at least one characteristic of thecell (such as some portion of the cell's discharge history or amorphological characteristic of the cell) and induces a discharge orcontrols the charging rate or current of the cell based on thecharacteristic(s). As an additional example, some embodiments aredirected to a cell management system that induces a discharge of thecell immediately (or at some earlier time) before and/or after acharging step of the cell, while the cell is connected to a chargingdevice.

In some embodiments, inducing a discharge of a cell may includedischarging the cell in response to a command from the controller. Insome embodiments, an induced discharge may be at a rate higher than anaverage discharge rate in the cell's discharge history. In someembodiments, an induced discharge may include discharging the cellwithout powering a load to perform a function, which may be done for thepurpose of altering the overall average discharge rate of the celland/or the average for a present charge/discharge cycle. In someembodiments, an induced discharge may be performed during a chargecycle, which may include multiple charging steps such as are shown inFIGS. 1B-1D.

Some embodiments, such as embodiments having multiple cells, aredirected to a battery management system that multiplexes cells such thatthe cells can be charged all at once (or with multiple cells dischargedat the same time) and discharged individually or in smaller sets. Thismay result in actual ratios of discharge rate to charge rate for thecells that improve their cycle life, while providing whatever outputrates that are desired or required for particular loads andapplications. Furthermore, the inventors have recognized and appreciatedthat discharging some but not all of the cells at once with homogeneouscurrent distribution may also improve their cycle life.

For example, with a battery having 4 cells, 1 cell could be dischargedat a time at 0.5 amps for 3 hours each, and then all 4 cells could becharged at 0.5 amps for 12 hours—such a configuration would provide anactual ratio of discharge rate to charge rate of 4:1, while the ratiofrom the user's perspective would be 1:1 because the cells aredischarged individually for 3 hours each (totaling 12 hours of dischargetime). The inventors have recognized and appreciated that such a batterymanagement system may actually improve the cycle life of batteries whilestill providing users what they desire or need from the batteries. Insome embodiments, the functionality providing this duo of benefits maybe hidden from users and may be integrated into the cell blocks and/orbatteries themselves.

The inventors have recognized and appreciated that the cycle life ofbatteries may be further improved by monitoring the cycles of the cellsand various properties (such as the duration of a connection between aload and a cell or cells currently connected to the load, or a morecomplex function considering multiple parameters) and selecting whichcells to discharge when based on this monitoring, especially compared toconventional techniques, which relied on much simpler selectionprocesses like “round robin” or considering a number of prior dischargecycles.

FIG. 1A depicts a representative cell management system 100. In someembodiments, representative system 100 may include a controller (e.g.,114) and an electrochemical cell (e.g., 121A). In some embodiments, cell121A may be present alone. In other embodiments, additional cells (e.g.,optional cells 121B and 121C in FIG. 1A) and/or additional cell sets(e.g., optional cell set 122 in FIG. 1A) may be present (e.g., to formbattery 120). Optionally, system 100 may include one or more sensors(e.g., 116). It should be appreciated that although only a singlecontroller 114 and a single sensor 116 are shown in FIG. 1A, anysuitable number of these components may be used. Any of numerousdifferent modes of implementation may be employed.

According to some embodiments, the cell 121A may include at least onelithium-metal electrode active material. Additionally, each set of cells(e.g., cell set 121) may include one or more cells (e.g., 121A-121C). Insome embodiments, each set of cells may have a single cell.Alternatively, each set of cells may include multiple cells and may forma cell “block,” or multiple sets of cells may together form a cellblock. Additionally, each cell (either in a battery, all the batteriesin a battery pack, or in a set of cells) or set of cells may utilize thesame electrochemistry. That is to say, in some embodiments, each cellmay make use of the same anode active material and the same cathodeactive material.

In some embodiments, such as embodiments having multiple cells, amultiplexing switch apparatus (not shown in FIG. 1A) may be included,such as described in relation to FIG. 1B below, and may include an arrayof switches, such as those further described in relation to FIGS. 3A and3B below. Additionally, the multiplexing switch apparatus may beconnected to each set of cells and/or to each cell individually. In someembodiments, the controller, such as 114, may use the multiplexingswitch apparatus to selectively discharge the cells or sets of cells.

In some embodiments, the controller (e.g., 114) may include one or moreprocessors, which may be of whatever complexity is suitable for theapplication. Alternatively or additionally, the controller may includean analog circuit and/or a less complex logic device than a processor ormicroprocessor.

In some embodiments, the controller may control the cell such that, forat least a portion of a charge cycle of the cell, the cell is charged ata charging rate or current that is lower than a discharging rate orcurrent of at least a portion of a previous discharge cycle. Forexample, the controller may cause the cell to be charged for somepercentage of the cell's re-charge capacity (e.g., anywhere from 1% to100% of re-charge capacity) at a charging rate or current that is onaverage at least 2 times lower than the discharging rate or current thathas been used on average for some percentage of the cell's dischargecapacity (e.g., anywhere from 1% to 100% of discharge capacity) (i.e.,the charging rate or current is half as fast as the discharging rate orcurrent). Alternatively or additionally, the controller may cause thecell to be charged at a charging rate or current that is at least 4times lower than the discharging rate (e.g., as a result of thiscontrolling, over the last discharge/charge cycle, the cell is chargedfor some percentage of the cell's re-charge capacity one-fourth as fastas the cell has been discharged for some percentage of the cell'sdischarge capacity). The inventors have recognized and appreciated thatsuch ratios of charge rate to discharge rate may improve the performanceand cycle life of a cell.

In some embodiments, controlling the cell may include controlling whenand how to start and stop charging and discharging, induce discharging,increase or decrease the rate or current of charging or discharging, andso on. For example, controlling charging or discharging of the cell mayinclude, respectively, starting charging or discharging, stoppingcharging or discharging, increasing or decreasing the rate or current ofcharging or discharging, and so on.

In some embodiments, the cell is charged such that, over a period oftime during which at least 5% (or at least 1%, or at least 10%, or atleast 15%, or at least 25%, or anywhere between) of the capacity of thecell is charged, the average charge rate or current is lower than theaverage discharge rate or current used to discharge at least 5% (or atleast 10%, or at least 15%, or at least 25%, or anywhere between) of thecell's capacity during a previous discharge cycle, which may be, forexample, the immediately preceding discharge cycle or an earlierdischarge cycle.

In some embodiments, a charging step is performed such that, for atleast 5% (or at least 10%, at least 25%, at least 50%, or at least 75%)of the cell's or battery's capacity, the average of the charging rateand/or current is less than 50% (or less than 35%, or less than 25%) ofan average discharging rate and/or current at which at least 5% (or atleast 10%, at least 25%, at least 50%, or at least 75%) of the cell's orbattery's capacity was discharged during a previous discharge step.

In certain embodiments, a charging step is performed such that, for atleast 5% (or at least 10%, at least 25%, at least 50%, or at least 75%)of the cell's or battery's capacity, the average of the charging rateand/or current is less than 50% (or less than 35%, or less than 25%) ofan average discharging rate and/or current at which at least 5% (or atleast 10%, at least 25%, at least 50%, or at least 75%) of the cell's orbattery's capacity was discharged during the immediately precedingdischarge step.

In some embodiments, an average discharging rate or current during theprevious discharge cycle may be equal to or less than an averagecharging rate or current during the charge cycle, and an averagedischarging rate or current during discharge of at least 5% of thedischarge capacity of the cell during the previous discharge cycle maybe at least 2 times higher (or may be 4 times higher) than the averagecharging rate or current during the charge cycle. The inventors haverecognized and appreciated that improvements described herein, such asimproved cell cycle life, can still be had even if the average dischargerate for the cell is the same or even slower than the charge rate, solong as during discharge of at least a portion (such as 5%) of thedischarge capacity of the cell during the previous discharge cycle, anaverage discharging rate or current is sufficiently higher than (such asat least double, triple, or quadruple) the average charging rate orcurrent during that time.

As used herein, when a cell is charged at multiple different rates overa given period of time (e.g., over a portion of a charging step, over anentire charging step, or over a series of charging steps), the averagecharging rate over that given period of time is calculated as follows:

${CR}_{Avg} = {\sum\limits_{i = 1}^{n}\;{\frac{{CCap}_{i}}{{CCap}_{Total}}{CR}_{i}}}$where CR_(Avg) is the average charging rate over the given period oftime, n is the number of different rates at which the cell is charged,CRi is the charging rate, CCap_(i) is the portion of the cell'sre-charge capacity that is charged at charging rate CR_(i) during thegiven period of time, and CCap_(Total) is the total of the cell'sre-charge capacity that is charged over the entire period of time. Toillustrate, if, during a charging step, a cell is charged from 0% to 50%of its re-charge capacity at a rate of 20 mAh/minute and then from 50%to 80% of its re-charge capacity at a rate of 10 mAh/minute, then theaverage charging rate during the charging step would be calculated as:

${CR}_{Avg} = {{{\frac{50\%}{80\%}\left( {20\mspace{14mu}{mAh}\text{/}\min} \right)} + {\frac{30\%}{80\%}\left( {10\mspace{14mu}{mAh}\text{/}\min} \right)}} = {16.25\mspace{14mu}{mAh}\text{/}{\min.}}}$

As used herein, when a cell is discharged at multiple different ratesover a given period of time (e.g., over a given charging step or seriesof charging steps), the average discharging rate over that given periodof time is calculated as follows:

${DR}_{Avg} = {\sum\limits_{i = 1}^{n}\;{\frac{{DCap}_{i}}{{DCap}_{Total}}{DR}_{i}}}$where DR_(Avg) is the average discharging rate over the given period oftime, n is the number of different rates at which the cell isdischarged, DRi is the discharging rate, DCap_(i) is the portion of thecell's discharge capacity that is discharged at discharging rate DR_(i)during the given period of time, and DCap_(Total) is the total of thecell's discharge capacity that is discharged over the entire period oftime. To illustrate, if, during a discharging step, a cell is dischargedfrom 90% to 50% of its discharge capacity at a rate of 25 mAh/minute andthen from 50% to 20% of its discharge capacity at a rate of 15mAh/minute, then the average discharging rate during the dischargingstep would be calculated as:

${DR}_{Avg} = {{{\frac{40\%}{70\%}\left( {25\mspace{14mu}{mAh}\text{/}\min} \right)} + {\frac{30\%}{70\%}\left( {15\mspace{14mu}{mAh}\text{/}\min} \right)}} = {20.71\mspace{14mu}{mAh}\text{/}{\min.}}}$

The inventors have recognized and appreciated that a number of factorsmay go into determining charge rates that may improve the performanceand cycle life of a cell such as a lithium metal cell, which may includerate of discharge, cell impedance, and/or cell State of Health (SOH). Insome embodiments, the controller may be aware of these factors becauseit may measure parameters or characteristics (such as via sensor 116)that can be used to determine each of them. The controller may directlyor indirectly measure charge and discharge current, Coulombs added orremoved, cell impedance (capacitive and resistive), and/or cellpressure, size, and/or thickness.

In some embodiments, the controller may monitor such characteristic(s)of the cell. For example, the characteristic(s) may include at least aportion of a discharge history of the cell. Alternatively oradditionally, the characteristic(s) may include at least onemorphological characteristic of the cell. The controller may monitor anyof these using sensor 116, such as a pressure sensor, a gauge to measurethickness, a sensor to measure or determine surface roughness and/orpits (such as pits in an anode), and/or a memory for storing cellcharge/discharge history. For example, a pressure sensor may be includedto measure uniaxial pressure and/or gas pressure (such as to determineif the cell generates an excessive amount of gas). Alternatively oradditionally, a gauge may be included to measure a thickness of thecell, and the controller may determine and monitor at least one rate ofincrease of the thickness.

In some embodiments, the controller may use this information, such asthe characteristic(s), to determine the charge method and/or rate to beused, which may include controlling rates or other parameters asdescribed herein. For example, the overall charging scheme may looksimilar to FIG. 1B, where the cell is discharged for time DT and chargedfor time CT. As shown in FIG. 1B, the cell is discharged briefly, thenfully charged at a lower current than for discharging, then dischargedbriefly, and topped back up with charge.

As another example, the overall charging scheme may look similar to FIG.1C, which shows a cell being discharged for time DT, charged for time CTat a lower current than for discharging, discharged again for time DT,charged again for time CT, then discharged again for time DT. In someembodiments, CT may correspond to just more than half of the total cellre-charge capacity, and DT may be a relatively short time determined bythe SOH of the cell.

In some embodiments, the controller may induce a discharge of the cell,such as any of the discharges shown in FIGS. 1B-1D. For example, thecontroller may induce a discharge of the cell immediately before abeginning of a charging step of the cell, such as in a form like thatshown in FIGS. 1B-1C. In some embodiments, the controller may cause suchan induced discharge or any of those described herein based on thecharacteristic(s) of the cell. Alternatively, the controller may performor cause any of these induced discharges based on other criteria, asdescribed herein. In some embodiments, the cell may remain connected tothe charging device during both the induced discharge and surroundingcharging step(s).

The inventors have recognized and appreciated that inducing a dischargeat the times described herein may improve the performance and cycle lifeof the cell because it may bring the ratio of discharge to charge ratesor currents to be closer to a desired asymmetric range, such as 2:1 or4:1. For example, if the cell has been discharged at a lower rate orcurrent than charging, such an induced discharge may be performed at amuch higher rate or current to improve the ratio, especially during aportion of the charge/discharge cycle. In some embodiments, thecontroller may induce a discharge of the cell at a first rate orcurrent, through at least a threshold capacity of the cell (such as atleast 5%, at least 10%, or at least 15% of the cell's discharge orre-charge capacity), before (such as immediately before or less than 10minutes before) a beginning of a charging step of the cell that chargesthe cell slower than the first rate or current. In some embodiments, thecontroller may induce a discharge at a rate or current that is higherthan an average discharging rate or current of a previous (such as thelatest) discharge cycle and/or discharging step or that is higher thanan average charging rate or current of a previous (such as the latest)charge cycle and/or charging step.

Alternatively or additionally, the controller may induce a discharge ofthe cell during (such as at an end of) a discharge cycle and/ordischarging step of the cell. In some embodiments, the controller mayinduce such a discharge at a higher rate or current than that of theexisting discharge or an average discharge of a previous dischargecycle. For example, a discharge may be induced at 400 mA, while theaverage discharge current of the most recent discharge cycle may havebeen 100 mA. Other examples may be found in Tables 1-4 below.

The controller may alternatively or additionally induce a discharge atan end of a charge cycle and/or a discharging step of the cell, such asin a form like that shown in FIG. 1C. In some embodiments, inducing adischarge at an end of a cycle may include inducing the discharge withinthe last 5% (or 10% or 15%) of the cycle.

The inventors have recognized and appreciated that inducing a dischargeof a cell in some or all of the situations described herein may reducephysical damage to the cell, such as pit formation and extension (e.g.,in the anode of the cell), and may even smooth out and undo someprevious damage to the cell.

The overall charging scheme may, as a further example, look similar toFIG. 1D, which shows a cell being first charged for time PCT, thendischarged for DT, and finally charged fully for CT. The inventors haverecognized and appreciated that when a cell is determined to have beenfully discharged, as may be the case for the cell in FIG. 1D, it wouldnot be advantageous to start with a discharge cycle and/or a dischargingstep.

In some embodiments, the controller may consider any of several factorswhen determining the cell State of Charge (SOC) and State of Health(SOH). For example, for cell impedance, the cell model can be simplifiedas shown in FIG. 1E, which shows a resistor in series (RS) with theparallel combination of a resistor (RP) and a capacitor (C1). Animpedance measurement may have two components: real and imaginary. Thereal component may be simply the DC resistance R=RS+RP. The imaginary(or reactive) component in this case may be XC, which may be affectedinversely by frequency:

${XC} = \frac{1}{2\pi\;{fc}}$where f is frequency and c is capacitance. Impedance (Z) may be found atany particular frequency, and the phase angle may be known or determinedas follows: Z=√{square root over (R²+XC²)}. Impedance may change bothwith SOC and SOH. The inventors have recognized and appreciated thatthese relationships may allow the controller to determine how to chargethe cell in order to provide improvements described herein.

The inventors have also recognized and appreciated that pulses ofcharge/discharge cycles and/or charging/discharging steps should not beapplied faster than a rate equal to about double or triple RC timeconstants, because at a faster rate, most of the energy may not beeffective in charging or discharging the cell. Rather, it may be mostlyreactive in nature and most of the energy may be returned by thecapacitance or dissipated in the resistance.

The inventors have further recognized and appreciated that a cell growsand shrinks in thickness with every cycle and that a portion of thegrowth is retained each cycle. This growth and shrinkage can be measuredby monitoring the pressure and/or size change of the cell directly.These are additional inputs that may be used when determining SOC andSOH, and they can also be used in determining how to charge the cell.

In some embodiments, the controller may control charging of the cellbased on the characteristic(s) of the cell. For example, if the cell hashad a discharge cycle or history of discharging at a certain dischargerate or current (such as 300 mA) at least for a portion of the previousdischarge cycle, the cell may be controlled to charge at a lower rate orcurrent (such as at 150 mA or 75 mA) for at least a portion of thecharge cycle.

In some embodiments including an induced discharge, the controller maycontrol the cell such that, for at least a portion of the charge cycle(such as 5% of the cycle), the cell is charged at a charging rate orcurrent that is lower than a discharging rate or current of at least aportion of a previous discharge cycle other than (i.e., not including)the induced discharge.

As another example, the controller may terminate usage of the cell if anapplied anisotropic pressure falls below a threshold, which may indicatethat the pressure applying system (examples of which are described inmore detail below) is damaged. For example, in some embodiments such athreshold may be 1% to 50% of nominal applied anisotropic pressure.Alternatively or additionally, the controller may terminate usage of thecell if pressure is too high or the thickness has been increasing fasterthan a threshold rate. For example, in some embodiments such a thresholdrate may be 1% to 3% of thickness increase or more per cycle.

FIG. 1F depicts a representative battery management system 100. In someembodiments, such as embodiments having multiple cells, representativesystem 100 may include a multiplexing switch apparatus (e.g., 112), acontroller (e.g., 114), one or more sensors (e.g., 116), and one or morebatteries (e.g., 120, 130, 140, 150, and so on). It should beappreciated that although only a single multiplexing switch apparatus112, controller 114, sensor 116, and only four batteries 120-150 areshown in FIG. 1F, any suitable number of these components may be used.Any of numerous different modes of implementation may be employed.Furthermore, although a label in the singular is used herein toreference a multiplexing switch apparatus, it should be appreciated thatthe components used for the multiplexing and switching described hereinmay be distributed across any suitable number of devices (e.g.,switches).

According to some embodiments, the battery or batteries may include atleast one lithium-metal battery. Additionally, the battery or batteries(e.g., 120-150) may respectively include one or more cell sets (e.g.,121-124, 131-132, 141-142, 151-152, and so on), referred to also as setsof cells. In some embodiments, two or more sets of cells are included ineach battery, such as 121-122 and so on. Additionally, each set of cells(e.g., cell set 121) may include one or more cells (e.g., 121A-121C). Insome embodiments, each set of cells may have a single cell.Alternatively, each set of cells may include multiple cells and may forma cell “block,” or multiple sets of cells may together form a cellblock. Additionally, each cell (either in a battery, all the batteriesin a battery pack, or in a set of cells) or set of cells may utilize thesame electrochemistry. That is to say, in some embodiments, each cellmay make use of the same anode active material and the same cathodeactive material.

In some embodiments, a multiplexing switch apparatus (e.g., 112) mayinclude an array of switches, such as those further described inrelation to FIGS. 3A and 3B below. Additionally, the multiplexing switchapparatus may be connected to each set of cells and/or to each cellindividually. In some embodiments, the controller, such as 114, may usethe multiplexing switch apparatus to selectively discharge the cells orsets of cells based on at least one criterion.

For example, the criterion may include a sequence in which to dischargethe cells or sets of cells, such as a predefined numbering or orderassociated with the sets of cells (e.g., starting with a first set,switching through each set to the last set, and then starting over withthe first set), and/or an order based on the cell(s) or set(s) of cellswith the next highest voltage or some other measure indicating the nextstrongest. The inventors have recognized and appreciated that using asequence, especially a predefined numbering, may reduce the complexityof the operations performed by the system (e.g., a controller that isnot a microprocessor) and may be usable by a wider array of systems.

Alternatively or additionally, the criterion may be context-sensitive,such as by considering any one or more of the following: a duration of aconnection between a load and a set of cells currently connected to theload (which may be at least 0.01 seconds in some embodiments), adelivered discharge capacity at the connection, and the value of afunction having one or more parameters. In certain embodiments, thecriterion may not include a number of prior discharge cycles of the setof cells.

In some embodiments, the function may have parameters such as any one ormore of the following: a capacity accumulated over several connectionsbetween the load and the set of cells, the delivered discharge capacityat the connection, a current of the set of cells, a voltage of the setof cells and/or of at least one other set of cells, a cutoff dischargevoltage of the set of cells, a power of the set of cells, an energy ofthe set of cells, a number of charge or discharge cycles of the set ofcells, an impedance of the set of cells, a rate of voltage fading of theset of cells during the connection, a temperature of the set of cells,and a pressure of the set of cells (e.g., the pressure on the cell(s)from their physical enclosure, which may indicate cell capacity and isdiscussed further below). According to some embodiments, the delivereddischarge capacity at a single connection may be in the range from 0.01%of nominal capacity to 100% (e.g., 95%) of set nominal capacity.

In some embodiments, a sensor (e.g., 116) may measure the criterionand/or any of the parameters of the function. For example, the sensormay include a current sensor that measures the current in amperes of agiven set of cells. It should be appreciated that the criterion may beplural or singular and may relate to the currently discharging set ofcells and/or may determine the next set of cells.

In some embodiments, the controller (e.g., 114) may include one or moreprocessors, which may be of whatever complexity is suitable for theapplication. For example, evaluating the function of the criterion insome embodiments may rely on a microprocessor forming part or all of thecontroller.

In some embodiments, the controller may use the multiplexing switchapparatus to selectively discharge and charge the cells or sets of cellsat different, programmable rates. For example, the controller may usethe multiplexing switch apparatus to selectively discharge the cells orsets of cells at a first rate at least 2 times higher than a second rateof charging the sets of cells (i.e., discharging twice as fast ascharging). Alternatively or additionally, the first rate of dischargingmay be at least 4 times higher than the second rate of charging the setsof cells (i.e., discharging four times as fast as charging). Theinventors have recognized and appreciated that such ratios of dischargerate to charge rate may improve the performance and cycle life of thecells.

According to some embodiments, the controller may temporally overlap thedischarge of the sets of cells. For example, before a given cell or setof cells ceases discharging, another cell or set of cells may begindischarging. In some embodiments, the controller may continue to providepower from the sets of cells during switching between different sets.The inventors have recognized and appreciated that this temporal overlapof discharging and continuation of power may maintain the powerrequirements of the load even during transition between different cellsof sets of cells, which may further improve the cycle life of thecell(s) compared to conventional techniques. Accordingly, multiple cellsmay discharge simultaneously during such an overlap. Additionally, suchan overlap may provide smoother transition of voltage than has beenpossible with conventional techniques.

In some embodiments, the load may be at least one component of avehicle. The vehicle may be any suitable vehicle, adapted for travel onland, sea, and/or air. For example, the vehicle may be an automobile,truck, motorcycle, boat, helicopter, airplane, and/or any other suitabletype of vehicle.

Alternatively or additionally, the controller may use the multiplexingswitch apparatus (e.g., 112) to connect the sets of cells to a load in atopology employed or required by the load.

In some embodiments, the controller may use the multiplexing switchapparatus (e.g., 112) to isolate a single set of cells for dischargingwhile other sets of cells are not discharging. Alternatively oradditionally, a single cell may be isolated at a time. For example, thecontroller may use the multiplexing switch apparatus to isolate a singleset of cells or a single cell for discharging while the other cells orsets of cells are not discharging. For a given cycle, each cell may bedischarged once before any cell is discharged twice, according to someembodiments (e.g., where sequential discharging is used, but not limitedto such embodiments).

As for charging, in some embodiments the controller may use themultiplexing switch apparatus to charge the sets of cells, and/or cellswithin a set, in parallel. For example, all the cells in the cell block,battery, or batteries may be charged in parallel at a rate one-fourth ofthe rate of discharge.

FIG. 2 depicts a representative battery pack 210. In some embodiments,representative battery pack 210 may include a switching control system(e.g., 218) and one or more batteries (e.g., 120, 130, 140, 150, and soon). It should be appreciated that although only a single switchingcontrol system 218 and only four batteries 120-150 are shown in FIG. 2 ,any suitable number of these components may be used. Any of numerousdifferent modes of implementation may be employed. Furthermore, althougha label in the singular is used herein to reference a switching controlsystem, it should be appreciated that the components used for thecontrol and switching described herein may be distributed across anysuitable number of devices (e.g., switches, controller(s), etc.).

In some embodiments, a switching control system (e.g., 218) may includean array of switches, such as those further described in relation toFIGS. 3A and 3B below, and it may include a controller. Additionally,the switching control system may be connected to each set of cellsand/or to each cell of the batteries individually, as discussedregarding FIG. 1F above. In some embodiments, the switching controlsystem may be integrated into the battery pack. Additionally, theswitching control system may control the switch(es) (such as in a switcharray) to discharge the cells or sets of cells sequentially, such as ina predefined order associated with the cells or sets of cells.Alternatively or additionally, the switching control system may controlthe switch(es) to discharge the cells or sets of cells based on any oneor more of the following: a duration of a connection between a load anda set of cells currently connected to the load (which may be at least0.01 seconds in some embodiments), a delivered discharge capacity at theconnection, and the value of a function. In certain embodiments, thebasis for the control may not include a number of prior discharge cyclesof the set of cells.

According to some embodiments, the switching control system may performany number of other functions, such as those of the controller describedin relation to FIGS. 1A and 1F above.

It should be appreciated that any of the components of representativesystem 100 or representative battery pack 210 may be implemented usingany suitable combination of hardware and/or software components. Assuch, various components may be considered a controller that may employany suitable collection of hardware and/or software components toperform the described function.

FIG. 3A depicts a representative battery management system 300. In someembodiments, representative system 300 may include any suitable numberof multi-cell blocks (e.g., 321-325), a battery cell block arrangementand balance switch configuration (e.g., 326), a battery managementmicrocontroller (e.g., 327), a battery system interface (e.g., 328),battery power terminals (e.g., 329), and a sensor (e.g., 360). Themulti-cell blocks may be connected to the battery cell block arrangementand balance switch configuration. The multi-cell blocks may also beconnected to the battery management microcontroller.

In some embodiments, the battery cell block arrangement and balanceswitch configuration may include switch multiplexing, which may connectthe cell blocks (e.g., 321-325) in the series, parallel,serial/parallel, or any other suitable topology required to meet thevoltage and current requirements of a given application or load.

According to some embodiments, the battery management microcontrollermay monitor and control the charging and discharging of the batterymanagement system to ensure the safe operation of the system and itscomponents. Additionally, the battery management microcontroller maycommunicate with a user (e.g., a consumer using the system to power aload) as well as with any suitable internal production, calibration, andtest equipment. For example, the battery management microcontroller maybe connected to the battery system interface (e.g., 328), which mayprovide the interface required for the battery managementmicrocontroller to communicate with the user as well as internalproduction, calibration, and test equipment, and any other suitableentity.

In some embodiments, the sensor may be connected to the battery cellblock arrangement and balance switch configuration, the batterymanagement microcontroller, and/or the battery power terminals, and itmay the measure attributes of the multi-cell blocks and/or any othercomponent of the system. For example, the sensor may measure attributesof the multi-cell blocks that form a criterion and/or any of theparameters of a function as described above. For example, the sensor mayinclude a current sensor that measures the current in amperes of a givenset of cells.

It should be appreciated that although battery cell block arrangementand balance switch configuration 326, battery management microcontroller327, battery system interface 328, and sensor 360 appear in singularform, and only five multi-cell blocks 321-325 are shown in FIG. 3A, anysuitable number of these components may be used and they may representmultiple components. Any of numerous different modes of implementationmay be employed. Indeed, although a label in the singular is used hereinto reference a battery cell block arrangement and balance switchconfiguration, it should be appreciated that the components used for thearrangement and balance switching described herein may be distributedacross any suitable number of devices (e.g., switches).

FIG. 3B depicts a representative cell set and corresponding components.In some embodiments, the representative cell set may include anysuitable number of cells (e.g., 321A-C) and may constitute a multi-cellblock, such as is described above. Additionally, the representative cellset may include cell multiplexing switches (e.g., 326A1), cell balanceswitches and resistors (e.g., 326A2), a cell block microcontroller(e.g., 327A), a battery management microcontroller interface (e.g.,328A), a sensor (e.g., 360A), and an input/output bus for the cell set(e.g., 321IO). In some embodiments, the cells may be connected to thecell balance switches and resistors, which may be connected to the cellmultiplexing switches.

In some embodiments, each cell (e.g., each of 321A-C) may be connectedto an array of the cell multiplexing switches, which may connect orisolate the given cell(s) from the input/output bus (e.g., 321IO), andwhich may connect or disconnect the given cell(s) to a balance resistor(e.g., one of the resistors in 326A2) that shares the balance bus withthe other cells. Additionally, in discharge mode one cell (e.g., 321A)may be connected to the input/output bus and disconnected from thebalance resistor. The remaining cells (e.g., 321B-C) may be disconnectedfrom the input/output bus and connected to the corresponding balanceresistor(s). Additionally, in charge mode for some embodiments, allcells (e.g., 321A-C) may be connected to the input/output bus anddisconnected from the balance resistors 326A2.

According to some embodiments, the cell block microcontroller (e.g.,327A) may generate switching waveforms to ensure that overlap anddeadband requirements for the switching is appropriate for theapplication or load. Additionally, the cell block microcontroller maydetermine the state required by the application or load by monitoringthe cell block's voltage and current, as well as by receivingcommunication from a battery management microcontroller (e.g., 327 inFIG. 3A), to which the cell block microcontroller may be connected viathe battery management microcontroller interface.

FIG. 3C is an exemplary cross-sectional schematic illustration of anelectrochemical system in which an anisotropic force is applied to anelectrochemical cell (e.g., 321A), according to one set of embodiments.The term “electrochemical cell” is used herein to generally refer to ananode, a cathode, and an electrolyte configured to participate in anelectrochemical reaction to produce power. An electrochemical cell canbe rechargeable or non-rechargeable.

In FIG. 3C, the system may include electrochemical cell 321A and, insome embodiments, a pressure distributor 334 containing a fluidassociated with electrochemical cell 321A. Pressure distributor 334 canbe configured such that an anisotropic force is applied to a componentof electrochemical cell 321A through pressure distributor 334. Forexample, in the set of embodiments illustrated in FIG. 3C, pressuretransmitter 336 can be configured to apply an anisotropic force topressure distributor 334, which in turn causes an anisotropic force tobe applied to at least one component (e.g., an electrode) ofelectrochemical cell 321A. The system can also include a substrate 332on which the electrochemical cell is positioned. Substrate 332 cancomprise, for example, a tabletop, a surface of a container in whichelectrochemical cell 321A is housed, or any other suitable surface.

Pressure distributor 334 can be associated with electrochemical cell321A in a variety of suitable configurations to produce the inventivesystems and methods described herein. As used herein, a pressuredistributor is associated with an electrochemical cell when at least aportion of a force that is applied to and/or through the pressuredistributor can be transmitted to a component of the electrochemicalcell. For example, in certain embodiments, a pressure distributor isassociated with an electrochemical cell when the pressure distributor isin direct contact with the electrochemical cell or a component thereof.Generally, a first article and a second article are in direct contactwhen the first article and the second article are directly touching. Forexample, in FIG. 3C, pressure distributor 334 and the electrochemicalcell 321A are in direct contact.

In certain embodiments, a pressure distributor is associated with theelectrochemical cell when the pressure distributor is in indirectcontact with at least one component of the electrochemical cell.Generally, a first article and a second article are in indirect contactwhen a pathway can be traced between the first article and the secondarticle that intersects only solid and/or liquid components. Such apathway can be in the form of a substantially straight line, in certainembodiments. A pressure distributor can be in indirect contact with anelectrochemical cell, in certain embodiments, when one or more solidand/or liquid materials are positioned between them, but a force canstill be transmitted to the electrochemical cell through the pressuredistributor.

In certain embodiments, a pressure distributor is associated with anelectrochemical cell when it is located within the boundaries of acontainer at least partially (e.g., completely) enclosing the componentsof the electrochemical cell. For example, in certain embodiments,pressure distributor 334 could be positioned between an electrode and acontainer at least partially enclosing the electrochemical cell. Incertain embodiments, pressure distributor 334 could be positionedbetween a current collector and a container at least partially enclosingthe electrochemical cell. In some embodiments, pressure distributor 334can be used as a current collector, for example, positioned next to anelectrode of the electrochemical cell and within a container at leastpartially containing the electrodes and electrolyte of the electriccell. This could be achieved, for example, by fabricating pressuredistributor 334 from a material (e.g., a metal such as a metal foil, aconductive polymer, and the like) that is sufficiently electricallyconductive to transport electrons to and/or from an electrode of theelectrochemical cell.

In some embodiments, a pressure distributor is associated with anelectrochemical cell when it is located outside the boundaries of acontainer at least partially (e.g., completely) enclosing the componentsof the electrochemical cell. For example, in certain embodiments,pressure distributor 334 could be positioned in direct or indirectcontact with an exterior surface of a container at least partiallyenclosing the electrodes and electrolyte of an electrochemical cell.

In certain embodiments, the pressure distributor can be located arelatively short distance from at least one electrode of anelectrochemical cell. For example, in certain embodiments, the shortestdistance between the pressure distributor and an electrode of theelectrochemical cell is less than about 10 times, less than about 5times, less than about 2 times, less than about 1 time, less than about0.5 times, or less than about 0.25 times the maximum cross-sectionaldimension of that electrode.

In some embodiments, a pressure distributor can be associated with aparticular electrode (e.g., an anode) of an electrochemical cell. Forexample, a pressure distributor can be in direct or indirect contactwith an electrode (e.g., an anode such as an anode comprising lithium)of an electrochemical cell. In certain embodiments, the pressuredistributor can be positioned outside a container at least partiallycontaining the electrode but still associated with the electrode, forexample, when only liquid and/or solid components separate the electrodefrom the pressure distributor. For example, in certain embodiments inwhich the pressure distributor is positioned in direct or indirectcontact with a container at least partially enclosing the electrode anda liquid electrolyte, the pressure distributor would be associated withthe electrode.

In certain embodiments, a force can be applied to electrochemical cell321A or a component of electrochemical cell 321A (e.g., an electrode ofthe electrochemical cell) through pressure distributor 334. As usedherein, a force is applied to a first component (e.g., anelectrochemical cell) through a second component (e.g., a pressuredistributor) when the second component at least partially transmits aforce from the source of the force to the first component.

A force can be applied to an electrochemical cell or a component thereofthrough a pressure distributor in a variety of ways. In certainembodiments, applying a force to a pressure distributor comprisesapplying a force to an external surface of the pressure distributor.This can be achieved, for example, via pressure transmitter 336. Forexample, in FIG. 3C, pressure transmitter 336 can be positioned to applyan anisotropic force to electrochemical cell 321A through pressuredistributor 334 by applying a force to surface 340 of pressuredistributor 334. As used herein, a first component is positioned toapply an anisotropic force to a second component when the first andsecond components are positioned such that at least a portion of a forcethat is applied to and/or through the first component can be transmittedto the second component. In certain embodiments, pressure transmitterand the pressure distributor are in direct contact. In some embodiments,one or more materials (e.g., one or more solid and/or liquid materials)are positioned between the pressure transmitter and the pressuredistributor, but a force can still be applied to the pressuredistributor by the pressure transmitter. In certain embodiments, thepressure transmitter and the pressure distributor can be in indirectcontact such that a continuous pathway can be traced through solidand/or liquid materials from the pressure distributor to theelectrochemical cell. Such a pathway can be substantially (e.g.,completely) straight, in certain embodiments.

In the set of embodiments illustrated in FIG. 3C, pressure transmitter336 and electrochemical cell 321A are positioned on opposite sides ofpressure distributor 334. Accordingly, when an anisotropic force (e.g.,an anisotropic force in the direction of arrow 150) is applied to and/orby pressure transmitter 336 to surface 340, the force can be transmittedthrough pressure distributor 334 onto surface 342 of electrochemicalcell 321A, and to the components of electrochemical cell 321A.

In some embodiments, applying a force to a pressure distributorcomprises applying a force to an internal surface of the pressuredistributor. For example, in certain embodiments, a force can be appliedthrough the pressure distributor to the electrochemical cell bymaintaining and/or increasing the pressure of the fluid within thepressure distributor. In the set of embodiments illustrated in FIG. 3C,a force can be applied through pressure distributor 334 toelectrochemical cell 321A by transporting additional fluid through aninlet (not shown) of pressure distributor 334 (e.g., by inflatingpressure distributor 334). In some such embodiments, when the pressurewithin a pressure distributor is maintained and/or increased, themovement of pressure transmitter can be restricted such that a force isproduced on an external surface of the electrochemical cell and/or on acomponent of the electrochemical cell (e.g., an active surface of anelectrode within the electrochemical cell). For example, in FIG. 3C, asadditional fluid is added to pressure distributor 334, pressuretransmitter 336 can be configured to restrict the movement of theboundaries of pressure distributor 334 such that a force is applied tosurface 342 of electrochemical cell 321A.

In certain embodiments, fluid can be added to pressure distributor 334before it is positioned between electrochemical cell 321A and pressuretransmitter 336. After the fluid has been added, pressure distributor334 can be compressed and positioned between electrochemical cell 321Aand pressure transmitter 336, after which, the compression of the fluidwithin pressure distributor 334 can produce a force that is applied tosurface 342 of electrochemical cell 321A (and, accordingly, to a surfaceof one or more components of the electrochemical cell, such as an activesurface of an electrode). One of ordinary skill in the art, given thepresent disclosure, would be capable of designing additional systems andmethods by which a force can be applied to an electrochemical cellthrough a pressure distributor.

The fluid within pressure distributor 334 can allow the pressure that istransmitted through pressure distributor 334 to be applied relativelyevenly across the surface 342 of electrochemical cell 321A (and,accordingly, relatively evenly across a surface of one or morecomponents of the electrochemical cell, such as an active surface of anelectrode). Not wishing to be bound by any particular theory, it isbelieved that a presence of a fluid within pressure distributor 334reduces and/or eliminates points of relatively high pressure on surface342 as fluid within relatively high pressure regions is transported toregions of relatively low pressure.

In some embodiments, the degree to which the pressure distributor evenlydistributes the force applied to electrochemical cell can be enhanced ifthe external surface of the pressure transmitter is appropriatelyaligned with an external surface of the electrochemical cell or acontainer thereof. For example, in the set of embodiments illustrated inFIG. 3C, external surface 340 of pressure transmitter 336 faces externalsurface 342 of electrochemical cell 321A. In certain embodiments, theexternal surface of the pressure transmitter is substantially parallelto the external surface of the electrochemical cell to which a force isapplied. For example, in the set of embodiments illustrated in FIG. 3C,external surface 340 of pressure transmitter 336 is substantiallyparallel to external surface 342 of electrochemical cell 321A. As usedherein, two surfaces are substantially parallel to each other when thetwo surfaces form angles of no greater than about 10 degrees. In certainembodiments, two substantially parallel surfaces form angles of nogreater than about 5 degrees, no greater than about 3 degrees, nogreater than about 1 degree, or no greater than about 0.1 degree.

The pressure distributor can have a variety of suitable forms. Incertain embodiments, the pressure distributor can comprise a bag orother suitable container in which a fluid is contained. In someembodiments, the pressure distributor can comprise a bellows that isconfigured to deform along the direction in which the force is appliedto the pressure distributor.

The pressure distributor container can be made of a variety ofmaterials. In certain embodiments, the pressure distributor containercan comprise a flexible material. For example, in certain embodiments,the pressure distributor container can comprise a polymer such aspolyethylene (e.g., linear low density and/or ultra-low densitypolyethylene), polypropylene, polyvinylchloride, polyvinyldichloride,polyvinylidene chloride, ethylene vinyl acetate, polycarbonate,polymethacrylate, polyvinyl alcohol, nylon, silicone rubber (e.g.,polydimethylsiloxane), and/or other natural or synthetic rubbers orplastics. In certain embodiments (e.g., in embodiments in which a gas isused as the fluid within the pressure distributor), the pressuredistributor container can include a metal layer (e.g., an aluminum metallayer), which can enhance the degree to which fluid (e.g., a gas) isretained within the pressure distributor. The use of flexible materialscan be advantageous, in certain embodiments, as they may allow forredistribution of the contents of the pressure distributor relativelyeasily, enhancing the degree to which the force is uniformly applied.

In some embodiments, the pressure distributor can comprise an elasticmaterial. In certain embodiments, the elasticity of the material fromwhich the pressure distributor is fabricated can be selected such thatthe pressure distributor transmits a desirable amount of a force appliedto the pressure distributor to an adjacent component. To illustrate, incertain cases, if the pressure distributor is made of a very flexiblematerial, a relatively high percentage of the force applied to thepressure distributor might be used to elastically deform the pressuredistributor material, rather than being transmitted to an adjacentelectrochemical cell. In certain embodiments, the pressure distributorcan be formed of a material having a Young's modulus of less than about1 GPa. One of ordinary skill in the art would be capable of measuringthe Young's modulus of a given material by performing, for example, atensile test (also sometimes referred to a tension test). Exemplaryelastic polymers (i.e., elastomers) that could be used include thegeneral classes of silicone polymers, epoxy polymers, and acrylatepolymers.

In certain embodiments, the pressure distributor comprises an enclosedcontainer containing a fluid. The pressure distributor can comprise anopen container containing a fluid, in certain embodiments. For example,in some embodiments, the pressure distributor comprises a containerfluidically connected to a device constructed and arranged to transportthe fluid through the pressure distributor, as described in more detailbelow.

A variety of fluids can be used in association with the pressuredistributor. As used herein, a “fluid” generally refers to a substancethat tends to flow and to conform to the outline of its container.Examples of fluids include liquids, gases, gels, viscoelastic fluids,solutions, suspensions, fluidized particulates, and the like. Typically,fluids are materials that are unable to withstand a static shear stress,and when a shear stress is applied, the fluid experiences a continuingand permanent distortion. The fluid may have any suitable viscosity thatpermits flow and redistribution of an applied force.

In certain embodiments, the fluid within the pressure distributorcomprises a gas (e.g., air, nitrogen, a noble gas (e.g., helium, neon,argon, krypton, xenon), a gas refrigerant, or mixtures of these). Incertain embodiments, the gas within the pressure distributor cancomprise a relatively high molecular weight (e.g., at least about 100g/mol), which can limit the degree to which gas permeates through thewalls of the pressure distributor. In some embodiments, the fluid withinthe pressure distributor comprises a liquid including, but not limitedto, water, an electrolyte (e.g., a liquid electrolyte similar oridentical to that used in the electrochemical cell), greases (e.g.,petroleum jelly, Teflon grease, silicone grease), oils (e.g., mineraloil), and the like. In certain embodiments, the fluid within thepressure distributor comprises a gel. Suitable gels for use within thepressure distributor include, but are not limited to, hydrogels (e.g.,silicone gel), organogels, or xerogels. In certain embodiments, thefluid comprises a fluidized bed of solid particles (e.g., sand, powders,and the like). Fluidization can be achieved, for example, by passing agas and/or a liquid through the particles and/or by vibrating asubstrate on which the particles are positioned such that the particlesmove relative to each other.

The fluid used in association with the pressure distributor can have anysuitable viscosity. In certain embodiments, a Newtonian fluid can beused within the pressure distributor, although some embodiments are notso limited, and non-Newtonian fluids (e.g., a shear thinning fluid, ashear thickening fluid, etc.) can also be used. In certain embodiments,the pressure distributor can contain a Newtonian fluid with asteady-state shear viscosity of less than about 1×10⁷ centipoise (cP),less than about 1×10⁶ cP, less than about 1×10⁵ cP less than about 1000cP, less than about 100 cP, less than about 10 cP, or less than about 1cP (and, in some embodiments, greater than about 0.001 cP, greater thanabout 0.01 cP, or greater than about 0.1 cP) at room temperature.

In certain embodiments, the fluid within the pressure distributor can beselected such that it is suitable for being transported into and/or outof the pressure distributor. For example, in certain embodiments, fluidmay be transported into the pressure distributor to apply an anisotropicforce to the electrochemical cell (e.g., by compressing the fluid withinthe pressure distributor when it is positioned between theelectrochemical cell and the pressure transmitter). As another example,a fluid may be transported into and/or out of a pressure distributor totransfer heat to and/or away from a component of the system.

Pressure transmitter 336 can also adopt a variety of configurations. Incertain embodiments, pressure transmitter 336 is moveable relative toelectrochemical cell 321A. In some such embodiments, a force can beapplied to electrochemical cell 321A through pressure distributor 334 bymoving pressure transmitter 336 closer to electrochemical cell 321Aand/or maintaining the separation between electrochemical cell 321A andpressure transmitter 336. As one particular example, in some embodimentsthe pressure transmitter 336 includes a compression spring, a firstapplicator structure, and a second applicator structure. Firstapplicator structure can correspond to, for example, a flat plate ofrigid material, or any other suitable structure. Second applicatorstructure can correspond to, for example, a second plate of rigidmaterial, a portion of a wall of a container in which theelectrochemical cell is housed, or any other suitable structure. In someembodiments, a force can be applied to surface 342 of electrochemicalcell 321A when a compression spring is compressed between applicatorstructure and applicator structure. In certain embodiments, Bellevillewashers, machine screws, pneumatic devices, weights, air cylinders,and/or hydraulic cylinders could be used in place of, or in addition to,the compression spring. In some embodiments, a force can be applied toan electrochemical cell using a constricting element (e.g., an elasticband, a turnbuckle band, etc.) arranged around one or more externalsurfaces of the electrochemical cell. A variety of suitable methods forapplying a force to an electrochemical cell are described, for example,in U.S. Patent Publication No. 2010/0035128 to Scordilis-Kelley et al.filed on Aug. 4, 2009, entitled “Application of Force in ElectrochemicalCells,” which is incorporated herein by reference in its entirety forall purposes.

In certain embodiments, pressure transmitter 336 is not substantiallymoveable relative to electrochemical cell 321A, and a force can beapplied to the electrochemical cell, for example, by pressurizing thepressure distributor 334. In some such embodiments, pressurizing thepressure distributor can result in the application of a force to theelectrochemical cell because the substantially immovable pressuretransmitter 336 restricts the movement of one or more of the boundariesof pressure distributor 334, thereby applying an anisotropic force toelectrochemical cell 321A.

In certain embodiments, pressure transmitter comprises all or part of asubstantially rigid structure (e.g., a package enclosing anelectrochemical cell), and the movement of the pressure transmitter canbe restricted by the degree to which the substantially rigid structureis inflexible. In certain embodiments, the pressure transmitter cancomprise a structure that is integrated with at least a portion of theother components of the system, which can restrict its movement. Forexample, in certain embodiments, the pressure transmitter can compriseat least a portion of one or more walls of a package within whichelectrochemical cell 321A and pressure distributor 334 are positioned.As one particular example, pressure transmitter 336 might form a firstwall of a package containing electrochemical cell 321A while substrate332 forms a second wall (e.g., opposite to the first wall) of thepackage. In certain embodiments, the movement of pressure transmitter336 can be restricted by applying a force within and/or on the pressuretransmitter such that its movement is restricted. In any of these cases,a force can be applied to the electrochemical cell, in certainembodiments, by adding fluid to and/or maintaining the amount of fluidwithin pressure distributor 334.

FIG. 3C illustrates a set of embodiments in which a single pressuretransmitter and a single pressure distributor are used to apply a forceto an electrochemical cell. In certain embodiments, however, more thanone pressure distributor and/or more than one pressure transmitter canbe employed. For example, in some embodiments, the system includes asecond pressure distributor positioned under electrochemical cell 321Aand a second pressure transmitter positioned under the second pressuredistributor. In certain embodiments, a substantially evenly distributedforce can be applied to an external surface of electrochemical cell 321Athrough the second pressure distributor, for example, by applying aforce to and/or through the second pressure transmitter and onto asurface of the second pressure distributor.

In some embodiments, fluid can be transported into and/or out of thepressure distributor to transport heat to and/or away fromelectrochemical cell 321A. For example, pressure distributor 334 mayinclude an inlet and an outlet configured to transport a fluid throughpressure distributor 334. As fluid is transported through pressuredistributor 334, it can absorb heat from electrochemical cell 321A andtransport it away from the system via the outlet. Any suitable devicecan be used to transport the fluid through the pressure distributor suchas, for example, a pump, a vacuum, or any other suitable device.

In certain embodiments, the fluid used in association with the pressuredistributor can be selected such that it cools or heats the system to adesired degree. For example, in certain embodiments, the fluid withinthe pressure distributor can comprise a coolant such as water, ethyleneglycol, diethylene glycol, propylene glycol, polyalkylene glycols(PAGs), oils (e.g., mineral oils, castor oil, silicone oils,fluorocarbon oils, and/or refrigerants (e.g., freons,chlorofluorocarbons, perfluorocarbons, and the like).

The embodiments described herein can be used with a variety ofelectrochemical cells. While primary (disposable) electrochemical cellsand secondary (rechargeable) electrochemical cells can be used inassociation with the embodiments described herein, some embodimentsadvantageously make use of secondary electrochemical cells, for example,due to the benefits provided by uniform force application during the(re)charging process. In certain embodiments, the electrochemical cellcomprises a lithium-based electrochemical cell such as a lithium-sulfurelectrochemical cell (and assemblies of multiple cells, such asbatteries thereof).

Although some embodiments can find use in a wide variety ofelectrochemical devices, an example of one such device is provided inFIG. 3D for illustrative purposes only. In FIG. 3D, a general embodimentof electrochemical cell 321A includes cathode 310, anode 312, andelectrolyte 314 in electrochemical communication with the cathode andthe anode.

In some cases, electrochemical cell 321A may optionally be at leastpartially contained by containment structure 316. Containment structure316 may comprise a variety of shapes including, but not limited to,cylinders, prisms (e.g., triangular prisms, rectangular prisms, etc.),cubes, or any other shape. In certain embodiments, a pressuredistributor can be associated with electrochemical cell 321A bypositioning the pressure distributor outside containment structure 316,in either direct or indirect contact with surface 318A and/or surface318B. When positioned in this way, the pressure distributor can beconfigured to apply a force, directly or indirectly, to surfaces 318Aand/or 318B of containment structure 316, as described above. In certainembodiments, a pressure distributor can be positioned between cathode310 and containment structure 316, or between anode 312 and containmentstructure 316. In some such embodiments, containment structure can actas a pressure transmitter and/or a separate pressure transmitter can beconfigured to apply a force to the pressure distributor via thecontainment structure.

A typical electrochemical cell system also would include, of course,current collectors, external circuitry, and the like. Those of ordinaryskill in the art are well aware of the many arrangements that can beutilized with the general schematic arrangement as shown in the figuresand described herein.

The components of electrochemical cell 321A may be assembled, in somecases, such that the electrolyte is located between the cathode and theanode in a planar configuration. For example, in the embodimentsillustrated in FIG. 3D, cathode 310 of electrochemical cell 321A issubstantially planar. A substantially planar cathode can be formed, forexample, by coating a cathode slurry on a planar substrate, such as ametal foil or other suitable substrate, which may be included in theassembly of electrochemical cell 321A (although not illustrated in FIG.3D) or removed from cathode 310 prior to assembly of the electrochemicalcell. In addition, in FIG. 3D, anode 312 is illustrated as beingsubstantially planar. A substantially planar anode can be formed, forexample, by forming a sheet of metallic lithium, by forming an anodeslurry on a planar substrate, or by any other suitable method.Electrolyte 314 is also illustrated as being substantially planar inFIG. 3D.

In certain embodiments, electrochemical cell 321A can comprise anelectrode that comprises a metal such as an elemental metal and/or ametal alloy. As one particular example, in certain embodiments,electrochemical cell 321A can comprise an anode comprising elementallithium (e.g., elemental lithium metal and/or a lithium alloy). Incertain embodiments, the anisotropic force applied to theelectrochemical cell is sufficiently large such that the application ofthe force affects the surface morphology of the metal within anelectrode of the electrochemical cell, as described in more detailbelow.

While FIG. 3D illustrates an electrochemical cell arranged in a planarconfiguration, it is to be understood that any electrochemical cellarrangement can be constructed, employing the principles of someembodiments, in any configuration. In addition to the shape illustratedin FIG. 3D, the electrochemical cells described herein may be of anyother shape including, but not limited to, cylinders, a foldedmulti-layer structure, prisms (e.g., triangular prisms, rectangularprisms, etc.), “Swiss-rolls,” non-planar multi-layered structures, etc.Additional configurations are described in U.S. patent application Ser.No. 11/400,025, filed Apr. 6, 2006, entitled, “Electrode Protection inboth Aqueous and Non-Aqueous Electrochemical Cells, includingRechargeable Lithium Batteries,” to Affinito et al., which isincorporated herein by reference in its entirety.

In some embodiments, the cathode and/or the anode comprise at least oneactive surface. As used herein, the term “active surface” is used todescribe a surface of an electrode that is in physical contact with theelectrolyte and at which electrochemical reactions may take place. Forexample, in the set of embodiments illustrated in FIG. 3D, cathode 310includes cathode active surface 320 and anode 312 includes anode activesurface 322.

In certain embodiments, the anisotropic force applied to a pressuretransmitter 336 and/or through pressure distributor 334 (and eventuallyin some cases to surface 342 of electrochemical cell 321A) comprises acomponent normal to the active surface of an electrode (e.g., an anodesuch as an anode containing lithium metal) within the electrochemicalcell. Accordingly, applying an anisotropic force through pressuredistributor 334 to the electrochemical cell can result in an anisotropicforce being applied to an active surface of an electrode (e.g., ananode) within the electrochemical cell. In the case of a planarelectrode surface, the applied force may comprise an anisotropic forcewith a component normal to the electrode active surface at the point atwhich the force is applied. For example, referring to the set ofembodiments illustrated in FIG. 3C and FIG. 3D, an anisotropic force inthe direction of arrow 370 may be applied to electrochemical cell 321Athrough pressure distributor 334. An anisotropic force applied in thedirection of arrow 370 would include a component 372 that is normal toanode active surface 322 and normal to cathode active surface 320. Inaddition, an anisotropic force applied in the direction of arrow 370would include a component 374 that is not normal (and is in factparallel) to anode active surface 322 and cathode active surface 320.

In the case of a curved surface (e.g., a concave surface or a convexsurface), the force applied to the electrochemical cell may comprise ananisotropic force with a component normal to a plane that is tangent tothe curved surface at the point at which the force is applied.

In one set of embodiments, systems and methods are configured such that,during at least one period of time during charge and/or discharge of thecell, an anisotropic force with a component normal to the active surfaceof an electrode (e.g., the anode) is applied to the electrochemicalcell. In some embodiments, the force may be applied continuously, overone period of time, or over multiple periods of time that may vary induration and/or frequency.

The magnitude of the applied force is, in some embodiments, large enoughto enhance the performance of the electrochemical cell. In certainembodiments, an electrode active surface (e.g., an anode active surface)and the anisotropic force may be together selected such that theanisotropic force affects surface morphology of the electrode activesurface to inhibit an increase in electrode active surface area throughcharge and discharge and wherein, in the absence of the anisotropicforce but under otherwise essentially identical conditions, theelectrode active surface area is increased to a greater extent throughcharge and discharge cycles. “Essentially identical conditions,” in thiscontext, means conditions that are similar or identical other than theapplication and/or magnitude of the force. For example, otherwiseidentical conditions may mean a cell that is identical, but where it isnot constructed (e.g., by brackets or other connections) to apply theanisotropic force on the subject electrochemical cell.

The electrode active surface and anisotropic force can be selectedtogether, to achieve results described herein, easily by those ofordinary skill in the art. For example, where the electrode activesurface is relatively soft, the component of the force normal to theelectrode active surface may be selected to be lower. Where theelectrode active surface is harder, the component of the force normal tothe electrode active surface may be greater. Those of ordinary skill inthe art, given the present disclosure, can easily select anodematerials, alloys, mixtures, etc. with known or predictable properties,or readily test the hardness or softness of such surfaces, and readilyselect cell construction techniques and arrangements to provideappropriate forces to achieve what is described herein. Simple testingcan be done, for example by arranging a series of active materials, eachwith a series of forces applied normal (or with a component normal) tothe active surface, to determine the morphological effect of the forceon the surface without cell cycling (for prediction of the selectedcombination during cell cycling) or with cell cycling with observationof a result relevant to the selection.

As noted above, in some embodiments, an anisotropic force with acomponent normal to an electrode active surface (e.g., of the anode) isapplied, during at least one period of time during charge and/ordischarge of the cell, to an extent effective to inhibit an increase insurface area of the electrode active surface relative to an increase insurface area absent the anisotropic force. The component of theanisotropic force normal to the electrode active surface may, forexample, define a pressure of at least about 20, at least about 25, atleast about 35, at least about 40, at least about 50, at least about 75,at least about 90, at least about 100, at least about 125, at leastabout 150, at least about 200, at least about 300, at least about 400,or at least about 500 Newtons per square centimeter. In certainembodiments, the component of the anisotropic force normal to the anodeactive surface may, for example, define a pressure of less than about500, less than about 400, less than about 300, less than about 200, lessthan about 190, less than about 175, less than about 150, less thanabout 125, less than about 115, or less than about 110 Newtons persquare centimeter. While forces and pressures are generally describedherein in units of Newtons and Newtons per unit area, respectively,forces and pressures can also be expressed in units of kilograms-forceand kilograms-force per unit area, respectively. One of ordinary skillin the art will be familiar with kilogram-force-based units, and willunderstand that 1 kilogram-force is equivalent to about 9.8 Newtons.

In certain embodiments, the component of the anisotropic force normal tothe active surface of an electrode within the electrochemical celldefines a pressure that is at least about 50%, at least about 75%, atleast about 100%, at least about 120% of the yield stress of thatelectrode (e.g., during charge and/or discharge of the electrochemicalcell). In certain embodiments, the component of the anisotropic forcenormal to the active surface of an electrode within the electrochemicalcell defines a pressure that is less than about 250% or less than about200% of the yield stress of that electrode (e.g., during charge and/ordischarge of the electrochemical cell). For example, in someembodiments, the electrochemical cell can comprise an anode (e.g., ananode comprising lithium metal and/or a lithium alloy), and thecomponent of an applied anisotropic force that is normal to the anodeactive surface can define a pressure that is at least about 50%, atleast about 75%, at least about 100%, or at least about 120% of theyield stress of the anode (and/or less than about 250% or less thanabout 200% of the yield stress of the anode). In some embodiments, theelectrochemical cell can comprise a cathode, and the component of theanisotropic force normal to the cathode active surface can define apressure that is at least about 50%, at least about 75%, at least about100%, or at least about 120% of the yield stress of the cathode (and/orless than about 250% or less than about 200% of the yield stress of thecathode).

In some cases, the anisotropic force can define a pressure that isrelatively uniform across one or more external surfaces of theelectrochemical cell and/or across one or more active surfaces ofelectrode(s) within the electrochemical cell. In some embodiments, atleast about 50%, at least about 75%, at least about 85%, at least about90%, at least about 95%, or at least about 98% of the area of one ormore external surfaces of an electrochemical cell and/or of the area ofone or more active surfaces of an electrode (e.g., anode) defines auniform area that includes a substantially uniform distribution ofpressure defined by an anisotropic force. In this context, a “surface ofan electrochemical cell” and a “surface of an electrode” refer to thegeometric surfaces of the electrochemical cell and the electrode, whichwill be understood by those of ordinary skill in the art to refer to thesurfaces defining the outer boundaries of the electrochemical cell andelectrode, for example, the area that may be measured by a macroscopicmeasuring tool (e.g., a ruler) and does not include the internal surfacearea (e.g., area within pores of a porous material such as a foam, orsurface area of those fibers of a mesh that are contained within themesh and do not define the outer boundary, etc.).

In some embodiments, a pressure is substantially uniformly distributedacross a surface when any continuous area that covers about 10%, about5%, about 2%, or about 1% of the uniform area (described in thepreceding paragraph) includes an average pressure that varies by lessthan about 25%, less than about 10%, less than about 5%, less than about2%, or less than about 1% relative to the average pressure across theentirety of the uniform area.

Stated another way, in some embodiments, at least about 50% (or at leastabout 75%, at least about 85%, at least about 90%, at least about 95%,or at least about 98%) of the area of a surface of the electrochemicalcell and/or of the active area of an electrode defines a first,continuous area of essentially uniform applied pressure, the first areahaving a first average applied pressure. In some cases, any continuousarea that covers about 10% (or about 5%, about 2%, or about 1%) of thefirst, continuous area of the surface of the electrochemical cell and/orof the electrode includes a second average applied pressure that variesby less than about 25% (or less than about 10%, less than about 5%, lessthan about 2%, or less than about 1%) relative to the first averageapplied pressure across the first, continuous area.

One of ordinary skill in the art would be capable of determining anaverage applied pressure within a portion of a surface, for example, bydetermining the force level applied at a representative number of pointswithin the surface portion, integrating a 3-dimensional plot of theapplied pressure as a function of position on the surface portion, anddividing the integral by the surface area of the surface portion. One ofordinary skill in the art would be capable of producing a plot of theapplied pressure across a surface portion by, for example, using aTekscan I-Scan system for measuring the pressure field.

The anodes of the electrochemical cells described herein may comprise avariety of anode active materials. As used herein, the term “anodeactive material” refers to any electrochemically active speciesassociated with the anode. For example, the anode may comprise alithium-containing material, wherein lithium is the anode activematerial. Suitable electroactive materials for use as anode activematerials in the anode of the electrochemical cells described hereininclude, but are not limited to, lithium metal such as lithium foil andlithium deposited onto a conductive substrate, and lithium alloys (e.g.,lithium-aluminum alloys and lithium-tin alloys). Methods for depositinga negative electrode material (e.g., an alkali metal anode such aslithium) onto a substrate may include methods such as thermalevaporation, sputtering, jet vapor deposition, and laser ablation.Alternatively, where the anode comprises a lithium foil, or a lithiumfoil and a substrate, these can be laminated together by a laminationprocess as known in the art to form an anode.

In one embodiment, an electroactive lithium-containing material of ananode active layer comprises greater than 50% by weight of lithium. Inanother embodiment, the electroactive lithium-containing material of ananode active layer comprises greater than 75% by weight of lithium. Inyet another embodiment, the electroactive lithium-containing material ofan anode active layer comprises greater than 90% by weight of lithium.Additional materials and arrangements suitable for use in the anode aredescribed, for example, in U.S. Patent Publication No. 2010/0035128 toScordilis-Kelley et al. filed on Aug. 4, 2009, entitled “Application ofForce in Electrochemical Cells,” which is incorporated herein byreference in its entirety for all purposes.

The cathodes in the electrochemical cells described herein may comprisea variety of cathode active materials. As used herein, the term “cathodeactive material” refers to any electrochemically active speciesassociated with the cathode. Suitable electroactive materials for use ascathode active materials in the cathode of the electrochemical cells ofsome embodiments include, but are not limited to, one or more metaloxides, one or more intercalation materials, electroactive transitionmetal chalcogenides, electroactive conductive polymers, sulfur, carbonand/or combinations thereof.

In some embodiments, the cathode active material comprises one or moremetal oxides. In some embodiments, an intercalation cathode (e.g., alithium-intercalation cathode) may be used. Non-limiting examples ofsuitable materials that may intercalate ions of an electroactivematerial (e.g., alkaline metal ions) include metal oxides, titaniumsulfide, and iron sulfide. In some embodiments, the cathode is anintercalation cathode comprising a lithium transition metal oxide or alithium transition metal phosphate. Additional examples includeLi_(x)CoO₂ (e.g., Li_(1.1)CoO₂), Li_(x)NiO₂, Li_(x)MnO₂, Li_(x)Mn₂O₄(e.g., Li_(1.05)Mn₂O₄), Li_(x)CoPO₄, Li_(x)MnPO₄, LiCo_(x)Ni_((1-x))O₂,and LiCo_(x)Ni_(y)Mn_((1-x-y))O₂ (e.g., LiNi_(1/3)Mn_(1/3)Co_(1/3)O₂,LiNi_(3/5)Mn_(1/5)Co_(1/5)O₂, LiNi_(4/5)Mn_(1/10)Co_(1/10)O₂,LiNi_(1/2)Mn_(3/10)Co_(1/5)O₂). X may be greater than or equal to 0 andless than or equal to 2. X is typically greater than or equal to 1 andless than or equal to 2 when the electrochemical cell is fullydischarged, and less than 1 when the electrochemical cell is fullycharged. In some embodiments, a fully charged electrochemical cell mayhave a value of x that is greater than or equal to 1 and less than orequal to 1.05, greater than or equal to 1 and less than or equal to 1.1,or greater than or equal to 1 and less than or equal to 1.2. Furtherexamples include Li_(x)NiPO₄, where (0<x≤1), LiMn_(x)Ni_(y)O₄ where(x+y=2) (e.g., LiMn_(1.5)Ni_(0.5)O₄), LiNi_(x)Co_(y)Al_(z)O₂ where(x+y+z=1), LiFePO₄, and combinations thereof. In some embodiments, theelectroactive material within the cathode comprises lithium transitionmetal phosphates (e.g., LiFePO₄), which can, in certain embodiments, besubstituted with borates and/or silicates.

As noted above, in some embodiments, the cathode active materialcomprises one or more chalcogenides. As used herein, the term“chalcogenides” pertains to compounds that contain one or more of theelements of oxygen, sulfur, and selenium. Examples of suitabletransition metal chalcogenides include, but are not limited to, theelectroactive oxides, sulfides, and selenides of transition metalsselected from the group consisting of Mn, V, Cr, Ti, Fe, Co, Ni, Cu, Y,Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, and Ir. In oneembodiment, the transition metal chalcogenide is selected from the groupconsisting of the electroactive oxides of nickel, manganese, cobalt, andvanadium, and the electroactive sulfides of iron. In one embodiment, acathode includes one or more of the following materials: manganesedioxide, iodine, silver chromate, silver oxide and vanadium pentoxide,copper oxide, copper oxyphosphate, lead sulfide, copper sulfide, ironsulfide, lead bismuthate, bismuth trioxide, cobalt dioxide, copperchloride, manganese dioxide, and carbon. In another embodiment, thecathode active layer comprises an electroactive conductive polymer.Examples of suitable electroactive conductive polymers include, but arenot limited to, electroactive and electronically conductive polymersselected from the group consisting of polypyrroles, polyanilines,polyphenylenes, polythiophenes, and polyacetylenes. Examples ofconductive polymers include polypyrroles, polyanilines, andpolyacetylenes.

In some embodiments, electroactive materials for use as cathode activematerials in electrochemical cells described herein includeelectroactive sulfur-containing materials. “Electroactivesulfur-containing materials,” as used herein, relates to cathode activematerials which comprise the element sulfur in any form, wherein theelectrochemical activity involves the oxidation or reduction of sulfuratoms or moieties. The nature of the electroactive sulfur-containingmaterials useful in the practice of some embodiments may vary widely, asknown in the art. For example, in one embodiment, the electroactivesulfur-containing material comprises elemental sulfur. In anotherembodiment, the electroactive sulfur-containing material comprises amixture of elemental sulfur and a sulfur-containing polymer. Thus,suitable electroactive sulfur-containing materials may include, but arenot limited to, elemental sulfur and organic materials comprising sulfuratoms and carbon atoms, which may or may not be polymeric. Suitableorganic materials include those further comprising heteroatoms,conductive polymer segments, composites, and conductive polymers.

In some embodiments, an electroactive sulfur-containing material of acathode active layer comprises greater than 50% by weight of sulfur. Inanother embodiment, the electroactive sulfur-containing materialcomprises greater than 75% by weight of sulfur. In yet anotherembodiment, the electroactive sulfur-containing material comprisesgreater than 90% by weight of sulfur.

The cathode active layers of some embodiments may comprise from about 20to 100% by weight of electroactive cathode materials (e.g., as measuredafter an appropriate amount of solvent has been removed from the cathodeactive layer and/or after the layer has been appropriately cured). Inone embodiment, the amount of electroactive sulfur-containing materialin the cathode active layer is in the range of 5-30% by weight of thecathode active layer. In another embodiment, the amount of electroactivesulfur-containing material in the cathode active layer is in the rangeof 20% to 90% by weight of the cathode active layer.

Additional materials suitable for use in the cathode, and suitablemethods for making the cathodes, are described, for example, in U.S.Pat. No. 5,919,587, filed May 21, 1997, entitled “Novel CompositeCathodes, Electrochemical Cells Comprising Novel Composite Cathodes, andProcesses for Fabricating Same,” and U.S. Patent Publication No.2010/0035128 to Scordilis-Kelley et al. filed on Aug. 4, 2009, entitled“Application of Force in Electrochemical Cells,” each of which isincorporated herein by reference in its entirety for all purposes.

A variety of electrolytes can be used in association with theelectrochemical cells described herein. In some embodiments, theelectrolyte may comprise a non-solid electrolyte, which may or may notbe incorporated with a porous separator. As used herein, the term“non-solid” is used to refer to materials that are unable to withstand astatic shear stress, and when a shear stress is applied, the non-solidexperiences a continuing and permanent distortion. Examples ofnon-solids include, for example, liquids, deformable gels, and the like.

The electrolytes used in electrochemical cells described herein canfunction as a medium for the storage and transport of ions, and in thespecial case of solid electrolytes and gel electrolytes, these materialsmay additionally function as a separator between the anode and thecathode. Any liquid, solid, or gel material capable of storing andtransporting ions may be used, so long as the material facilitates thetransport of ions (e.g., lithium ions) between the anode and thecathode. Exemplary materials suitable for use in the electrolyte aredescribed, for example, in U.S. Patent Publication No. 2010/0035128 toScordilis-Kelley et al. filed on Aug. 4, 2009, entitled “Application ofForce in Electrochemical Cells,” which is incorporated herein byreference in its entirety for all purposes.

U.S. application Ser. No. 16/527,903, filed Jul. 31, 2019, and entitled“Multiplexed Charge Discharge Battery Management System” is incorporatedherein by reference in its entirety for all purposes.

The following documents are incorporated herein by reference in theirentireties for all purposes: U.S. Pat. No. 7,247,408, filed May 23,2001, entitled “Lithium Anodes for Electrochemical Cells”; U.S. Pat. No.5,648,187, filed Mar. 19, 1996, entitled “Stabilized Anode forLithium-Polymer Batteries”; U.S. Pat. No. 5,961,672, filed Jul. 7, 1997,entitled “Stabilized Anode for Lithium-Polymer Batteries”; U.S. Pat. No.5,919,587, filed May 21, 1997, entitled “Novel Composite Cathodes,Electrochemical Cells Comprising Novel Composite Cathodes, and Processesfor Fabricating Same”; U.S. patent application Ser. No. 11/400,781,filed Apr. 6, 2006, published as U. S. Pub. No. 2007-0221265, andentitled “Rechargeable Lithium/Water, Lithium/Air Batteries”;International Patent Apl. Serial No.: PCT/US2008/009158, filed Jul. 29,2008, published as International Pub. No. WO/2009017726, and entitled“Swelling Inhibition in Lithium Batteries”; U.S. patent application Ser.No. 12/312,764, filed May 26, 2009, published as U.S. Pub. No.2010-0129699, and entitled “Separation of Electrolytes”; InternationalPatent Apl. Serial No.: PCT/US2008/012042, filed Oct. 23, 2008,published as International Pub. No. WO/2009054987, and entitled “Primerfor Battery Electrode”; U.S. patent application Ser. No. 12/069,335,filed Feb. 8, 2008, published as U.S. Pub. No. 2009-0200986, andentitled “Protective Circuit for Energy-Storage Device”; U.S. patentapplication Ser. No. 11/400,025, filed Apr. 6, 2006, published as U.S.Pub. No. 2007-0224502, and entitled “Electrode Protection in bothAqueous and Non-Aqueous Electrochemical Cells, including RechargeableLithium Batteries”; U.S. patent application Ser. No. 11/821,576, filedJun. 22, 2007, published as U.S. Pub. No. 2008/0318128, and entitled“Lithium Alloy/Sulfur Batteries”; patent application Ser. No.11/111,262, filed Apr. 20, 2005, published as U.S. Pub. No.2006-0238203, and entitled “Lithium Sulfur Rechargeable Battery FuelGauge Systems and Methods”; U.S. patent application Ser. No. 11/728,197,filed Mar. 23, 2007, published as U.S. Pub. No. 2008-0187663, andentitled “Co-Flash Evaporation of Polymerizable Monomers andNon-Polymerizable Carrier Solvent/Salt Mixtures/Solutions”;International Patent Apl. Serial No.: PCT/US2008/010894, filed Sep. 19,2008, published as International Pub. No. WO/2009042071, and entitled“Electrolyte Additives for Lithium Batteries and Related Methods”;International Patent Apl. Serial No.: PCT/US2009/000090, filed Jan. 8,2009, published as International Pub. No. WO/2009/089018, and entitled“Porous Electrodes and Associated Methods”; U.S. patent application Ser.No. 12/535,328, filed Aug. 4, 2009, published as U.S. Pub. No.2010/0035128, and entitled “Application of Force In ElectrochemicalCells”; U.S. patent application Ser. No. 12/727,862, filed Mar. 19,2010, entitled “Cathode for Lithium Battery”; U.S. patent applicationSer. No. 12/471,095, filed May 22, 2009, entitled “Hermetic SampleHolder and Method for Performing Microanalysis Under ControlledAtmosphere Environment”; U.S. patent application Ser. No. 12/862,513,filed on Aug. 24, 2010, entitled “Release System for Electrochemicalcells (which claims priority to Provisional Patent Apl. Ser. No.61/236,322, filed Aug. 24, 2009, entitled “Release System forElectrochemical Cells”); U.S. Provisional Patent Apl. Ser. No.61/376,554, filed on Aug. 24, 2010, entitled “ElectricallyNon-Conductive Materials for Electrochemical Cells;” U.S. Provisionalpatent application Ser. No. 12/862,528, filed on Aug. 24, 2010, entitled“Electrochemical Cell;” U.S. patent application Ser. No. 12/862,563,filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0070494,entitled “Electrochemical Cells Comprising Porous Structures ComprisingSulfur”; U.S. patent application Ser. No. 12/862,551, filed on Aug. 24,2010, published as U.S. Pub. No. 2011/0070491, entitled “ElectrochemicalCells Comprising Porous Structures Comprising Sulfur”; U.S. patentapplication Ser. No. 12/862,576, filed on Aug. 24, 2010, published asU.S. Pub. No. 2011/0059361, entitled “Electrochemical Cells ComprisingPorous Structures Comprising Sulfur”; U.S. patent application Ser. No.12/862,581, filed on Aug. 24, 2010, published as U.S. Pub. No.2011/0076560, entitled “Electrochemical Cells Comprising PorousStructures Comprising Sulfur”; U.S. Patent Apl. Ser. No. 61/385,343,filed on Sep. 22, 2010, entitled “Low Electrolyte ElectrochemicalCells”; and U.S. patent application Ser. No. 13/033,419, filed Feb. 23,2011, entitled “Porous Structures for Energy Storage Devices”. All otherpatents and patent applications disclosed herein are also incorporatedby reference in their entirety for all purposes.

FIG. 4A depicts a representative high-level process 400A for controllinga charging rate or current of a cell. The acts of representative process400A are described in detail in the paragraphs that follow.

In some embodiments, representative process 400A may include act 430A,wherein an electrochemical cell (such as electrochemical cell 121Adescribed above) may be controlled to be, for at least a portion of acharge cycle, charged at a charging rate or current that is lower than adischarging rate or current of at least a portion of a previousdischarge cycle, as described herein.

In some embodiments, process 400A may then end or repeat as necessary,such as for more charge/discharge cycles.

FIG. 4B depicts a representative process 400B for controlling a chargingrate or current of a cell (such as electrochemical cell 121A describedabove). The acts of representative process 400B are described in detailin the paragraphs that follow.

In some embodiments, representative process 400B may include act 410,wherein characteristic(s) of a cell may be monitored (e.g., by acontroller such as 114 and a sensor 116 as described above), asdescribed herein.

In some embodiments, representative process 400B may then optionallyproceed to act 420, wherein at least one threshold may be considered todetermine if it has been met, as described herein. For example, thethreshold may be a threshold measurement of the monitoredcharacteristic(s), such as a threshold amount (or rate or current) ofdischarging in the discharge history, a pressure measurement on thecell, and so on.

In some embodiments, if the threshold has been met, representativeprocess 400B may then proceed to act 430A, wherein the cell may becontrolled (e.g., by controller 114) to be charged at a charging rate orcurrent lower than a discharging rate or current for a portion of thecell's discharge cycle. For example, if the cell has had a dischargecycle or history of discharging at 300 mA, the cell may be controlled tocharge at 150 mA or less, as described herein. Alternatively, if thethreshold has not been met, the characteristic(s) may continue to bemonitored.

In some embodiments, representative process 400B may then optionallyproceed to act 431B, wherein an induced discharge of the cell may becaused by the controller. An induced discharge may be caused at varioustimes and for various reasons, as described herein.

In some embodiments, representative process 400B may then optionallyproceed to any of acts 432 or 434. For example, if process 400B proceedsfrom act 431B to act 432, the cell may be controlled to charge at acharging rate at least 2 times lower than its discharging rate, asdescribed herein.

Alternatively or additionally, process 400B may proceed from act 431B toact 434, wherein the cell may be controlled to charge at a charging rate4 times lower than its discharging rate, as described herein.

In some embodiments, process 400B may then end or repeat as necessary,such as for more charge/discharge cycles.

It should be appreciated that any of acts 432 and/or 434 may actually beintegral to act 430A, although they are represented as separate acts inFIG. 4B.

FIG. 4C depicts a representative high-level process 400C for inducingdischarge of a cell. The acts of representative process 400C aredescribed in detail in the paragraphs that follow.

In some embodiments, representative process 400C may include act 430C,wherein an induced discharge of a electrochemical cell (such aselectrochemical cell 121A described above) may be caused before and/orafter a charging step, as described herein.

In some embodiments, process 400C may then end or repeat as necessary,such as for more charge/discharge cycles.

FIG. 4D depicts a representative process 400D for inducing discharge ofa cell. The acts of representative process 400D are described in detailin the paragraphs that follow.

In some embodiments, representative process 400D may optionally includeact 410, wherein characteristic(s) of a cell may be monitored asdescribed herein.

In some embodiments, representative process 400D may then optionallyproceed to act 420, wherein at least one threshold may be considered todetermine if it has been met. For example, the threshold may be athreshold measurement of the monitored characteristic(s), such as athreshold amount (or rate or current) of discharging in the dischargehistory, a pressure measurement on the cell, a thickness or size of thecell, and so on.

In some embodiments, if the threshold has been met, representativeprocess 400D may then proceed to act 430C, an induced discharge of thecell may be caused by the controller (e.g., by controller 114), asdescribed herein. For example, the threshold may be met if acharge/discharge history of the cell shows that the discharge cycle hasended, the discharge cycle and/or a discharging step is still inprogress, a charge cycle has ended, or a charge cycle and/or chargingstep is about to begin, as described herein. Alternatively, if thethreshold has not been met, the characteristic(s) may continue to bemonitored.

In some embodiments, representative process 400D may then optionallyproceed to act 431D, wherein the cell may be controlled to be, for atleast a portion of a charge cycle, charged at a charging rate or currentthat is lower than a discharging rate or current of at least a portionof a previous discharge cycle, as described herein.

In some embodiments, representative process 400D may then optionallyproceed to any of acts 432 or 434. For example, if process 400D proceedsfrom act 431D to act 432, the cell may be controlled to charge at acharging rate at least 2 times lower than its discharging rate.

Alternatively or additionally, process 400D may proceed from act 431D toact 434, wherein the cell may be controlled to charge at a charging rate4 times lower than its discharging rate.

In some embodiments, process 400D may then end or repeat as necessary,such as for more charge/discharge cycles.

It should be appreciated that any of acts 432 and/or 434 may actually beintegral to act 430C, although they are represented as separate acts inFIG. 4D.

FIG. 5A depicts a representative process 500A for monitoring cellcharacteristic(s) and inducing discharge or controlling the charge rateor current of the cell. The acts of representative process 500A aredescribed in detail in the paragraphs that follow.

In some embodiments, representative process 500A may include act 510,wherein characteristic(s) of a cell may be monitored (e.g., by acontroller such as 114 and a sensor 116 as described above), asdescribed herein.

In some embodiments, process 500A may then proceed from act 510 to act530, wherein, based on the monitoring in act 510, an induced dischargeof the cell and/or controlled charging of the cell may be caused by thecontroller, as described herein.

In some embodiments, process 500A may then end or repeat as necessary.

FIG. 5B depicts a representative process 500B for monitoring cellcharacteristic(s) and inducing discharge or controlling the charge rateor current of the cell. The acts of representative process 500B aredescribed in detail in the paragraphs that follow.

In some embodiments, representative process 500B may include act 510,wherein characteristic(s) of a cell may be monitored (e.g., by acontroller such as 114 and a sensor 116 as described above).

In some embodiments, representative process 500B may then optionallyproceed to act 520, wherein at least one threshold may be considered todetermine if it has been met, as described herein. For example, thethreshold may be a threshold measurement of the monitoredcharacteristic(s), such as a threshold amount (or rate or current) ofdischarging in the discharge history, a pressure measurement on thecell, a thickness or size of the cell, and so on.

In some embodiments, if the threshold has been met, representativeprocess 500B may then proceed to act 530, wherein an induced dischargeof the cell may be caused by the controller (e.g., by controller 114),as described herein. For example, the threshold may be met if acharge/discharge history of the cell shows that the discharge cycle hasended, the discharge cycle and/or a discharging step is still inprogress, a charge cycle has ended, or a charge cycle and/or chargingstep is about to begin, as described herein. Alternatively, if thethreshold has not been met, the characteristic(s) may continue to bemonitored.

In some embodiments, representative process 500B may then optionallyproceed to any of acts 532 or 534. For example, if process 500B proceedsfrom act 530 to act 532, the cell may be controlled to charge at acharging rate at least 2 times lower than its discharging rate.

Alternatively or additionally, process 500B may proceed from act 530 toact 534, wherein the cell may be controlled to charge at a charging rate4 times lower than its discharging rate.

In some embodiments, process 500B may then end or repeat as necessary.

It should be appreciated that any of acts 532 and/or 534 may actually beintegral to act 530, although they are represented as separate acts inFIG. 5B.

The inventors have recognized and appreciated that some embodimentsdescribed above may produce results showing various improvements overconventional techniques when implemented.

In the following Examples 1-5 and Tables 1-4, cells are cycled underpressure of 10-12 kg/cm².

Example 1: Example 1 shows that cycle life was short when cells werecycled at the same charge and discharge rates (currents or times) in thewide range of rates. Cells with NCM111 cathode, 15 μm vapor-depositedlithium anode, and an electrolyte were cycled under 10 kg/cm² pressure.The electrolyte included a 1 molar solution of lithiumhexafluorophosphate in a 2:1 weight ratio of ethylene carbonate todimethyl carbonate. Total cell active electrodes area was 99.4 cm² andcell capacity was 200 mAh. Cell were charged to 4.35 V and discharged to3.2 V at currents in Table 1 below. Charge and discharge current wereequal. All cells showed short cycle life of 38-56 cycles for the rangeof charge discharge currents from 40 to 200 mA (5 times differentcurrents).

TABLE 1 Discharge Charge Cycle Life mA mA to 110 mAh  40  40 56  67  6744 150 150 38 200 200 38

Example 2: Example 2 shows that cycle life improved when dischargecurrent was fixed but charge currents were substantially lower. Higherdischarge/charge currents ratio led to longer cycle life.

Cells similar to Example 1 but with NCM622 cathode. Cell capacity was330 mAh. Cells were charged to 4.35 V and discharged to 3.2 V atcurrents in Table 2 below.

TABLE 2 Discharge Discharge/Charge Cycle Life to 250 mA Charge mACurrent Ratio mAh 300 100 3 96 300 50 6 140 300 40 7.5 146 300 30 10 159

Cycle life in Table 2 increased with higher discharge/charge currentratio. The biggest gain was for 3-6 ratio with diminishing additionalgain at higher ratio values and respectively longer charge.

Example 3: Example 3 shows that cycle life improved when charge currentwas fixed but discharge current was substantially higher. Higherdischarge/charge currents ratio led to longer cycle life.

Cells are similar to Example 2 but with electrolyte LiIon1401. Cellcapacity was 330 mAh. Cells were charged to 4.35 V and discharged to 3.2V at currents in Table 3 below.

TABLE 3 Discharge Discharge/Charge Cycle Life to 250 mA Charge mACurrent Ratio mAh  75 75 1  54 300 75 4 334

Change of discharge/charge currents ratio from 1 to 4 at fixed chargecurrent lead to dramatic, 6-fold cycle life improvement.

Example 4: Example 4 shows that cycle life improved when charge currentwas fixed and discharge current was substantially higher but was notnecessarily continuous. The cell was discharged at conditions whendischarge was periodically suspended for a certain period of time andresumed again.

Cells are similar to Example 3. Cell capacity was 330 mAh. Cells werecharged to 4.35 V and discharged to 3.2 V at currents in Table 3 below.Charge and discharge currents of 100 mA were continuous.

Discharge process at 400 mA was not continuous. Discharge at 400 mAlasted for 10 s, then was suspended for 30 s and resumed again. Thisprocess was periodical. Cycle life data obtained at these two processesare in Table 4.

TABLE 4 Discharge Discharge/Charge Cycle Life to 250 mA Charge mACurrent Ratio mAh 100 100 1  51 400 100 4 277

Example 5: Example 5 shows that cycle life improved only if higherdischarge/charge current ratio is applicable for substantial part ofdischarge time or capacity. If higher current discharge conditions arejust a small portion of entire discharge time the cycle life gain is notsubstantial.

Cells are similar to Example 4 but with NCM721 cathode. Cell capacitywas 360 mAh. Cells were charged to 4.4 V and discharged to 3.2 V.

The first portion of the cells experienced equal 100 mA charge anddischarge currents and delivered cycle life of 43 cycle at 250 mAhcutoff.

The second portion of the cells was charged at constant current of 100mA and discharged at two steps: 100 mA to 95% of capacity and then at400 mA to get remaining 5% of capacity.

The cycle life of these cells was 52 cycles. This was 9 cycles or ˜21%of cycle life gain based on higher discharge/charge current ratio of 4being applied for 5% of total discharge capacity. The inventors haverecognized and appreciated that better cycle life can be expected with5% of discharge capacity obtained at higher discharge/charge currentratio, such as where an average discharging rate or current during theprevious discharge cycle is equal to or less than an average chargingrate or current during the charge cycle, and an average discharging rateor current during discharge of at least 5% of the discharge capacity ofthe cell during the previous discharge cycle is at least 2 times higheror is 4 times higher than the average charging rate or current duringthe charge cycle.

FIG. 6A depicts a representative high-level process 600A for dischargingsets of cells of a battery. The acts of representative process 600A aredescribed in detail in the paragraphs that follow.

In some embodiments, representative process 600A may include act 630A,wherein sets of cells in a battery may be selectively discharged basedon at least one criterion using a multiplexing switch apparatus (such asmultiplexing switch apparatus 112 described above). Additionally, themultiplexing switch apparatus may be connected to two or more sets(e.g., 121, 122, 123, and/or 124) of cells (e.g., 121A-C) of at leastone battery (e.g., 120-150). Each set of cells may comprise one or morecells.

In some embodiments, process 600A may then end or repeat as necessary.

FIG. 6B depicts a representative high-level process 600B for dischargingsets of cells of a battery. The acts of representative process 600B aredescribed in detail in the paragraphs that follow.

In some embodiments, representative process 600B optionally may begin atact 610, wherein the multiplexing switch apparatus may be used toconnect the sets of cells to a load in a topology employed by the load.The batteries (e.g., 120-150) may include sets (e.g., 121, 122, 123,and/or 124) of the cells (e.g., 121A-C), and each set of cells maycomprise one or more cells. For example, the multiplexing switchapparatus may connect the cells to the load in series, parallel,serial/parallel, or any other suitable topology required to meet thevoltage and current requirements of the load or the desires of the givenapplication or user.

In some embodiments, representative process 600B may then optionallyproceed to act 620, wherein at least one criterion, and/or someparameter of a criterion, may be measured or otherwise monitored inrelation to the cells of the battery or batteries, which may already bedischarging or have discharged at least one cell or set of cells, todetermine whether the criterion has been met.

For example, a sensor (such as 116 in FIGS. 1A and 1F) may measure thedelivered discharge capacity at a connection between a load and a set ofcells currently connected to the load, or it may measure the current ofthe set of cells. Alternatively or additionally, the sensor may measureany of the following: a duration of the connection (which may be atleast 0.01 seconds in some embodiments), a capacity accumulated overseveral connections between the load and the set of cells, a voltage ofthe set of cells and/or of at least one other set of cells, a cutoffdischarge voltage of the set of cells, a power of the set of cells, anenergy of the set of cells, a number of charge or discharge cycles ofthe set of cells, an impedance of the set of cells, a rate of voltagefading of the set of cells during the connection, a temperature of theset of cells, and a pressure of the set of cells.

In some embodiments, the criterion may include a sequence in which todischarge the cells or sets of cells. Alternatively or additionally, thecriterion may be the value of a function that has any of the above asparameters. According to some embodiments, the criterion does notinclude a number of prior discharge cycles of the sets of cells.

In some embodiments, if the criterion has been met, representativeprocess 600B may then proceed to act 630, wherein the next set of cellsin the battery may be selectively discharged based on the criterionusing a multiplexing switch apparatus (such as multiplexing switchapparatus 112 described above). For example, if the current dischargingset of cells has met whatever criterion or criteria is required, thatset of cells may be disconnected and the next set of cells may beconnected (where the next set may be determined by a criterion orcriteria which may be the same or different from those discussed above)as described herein. Alternatively, if the criterion has not been met,it may continue to be monitored. According to some embodiments, theconnection between a single cell and the load may be at least 0.01seconds in duration. The inventors have recognized and appreciated thata shorter connection duration than 0.01 seconds may surprisingly producemore noise than at 0.01 seconds and may not allow the electrochemistryof the cell to accomplish anything non-negligible.

In some embodiments, representative process 600B may then optionallyproceed to act 631, wherein the multiplexing switch apparatus may beused to isolate a single set of cells for discharging while other setsof cells are not discharging. For example, when a controller (e.g., 114of FIGS. 1A and 1F) determines that cell 121B should be discharged, itmay cause the multiplexing switch apparatus to isolate cell 121B fordischarging while cells 121A and 121C are not discharging.

In some embodiments, representative process 600B may then optionallyproceed to any of acts 632, 634, 636, and/or 638. For example, ifprocess 600B proceeds from act 631 to act 632, the multiplexing switchapparatus may be used to selectively discharge the sets of cells at afirst rate at least 2 times higher than a second rate of charging thesets of cells.

Alternatively or additionally, process 600B may proceed from act 631 toact 634, wherein the multiplexing switch apparatus may be used toselectively discharge the sets of cells at a first rate at least 4 timeshigher than a second rate of charging the sets of cells.

Alternatively or additionally, process 600B may proceed from act 631 toact 636, wherein discharge of the sets of cells may be temporallyoverlapping, such as by using the multiplexing switch apparatus asdiscussed above.

Alternatively or additionally, process 600B may proceed from act 631 toact 638, wherein power may continue to be provided from the sets ofcells during switching between different sets.

It should be appreciated that any of acts 631, 632, 634, 636, and/or 638may actually be integral to act 630, although they are represented asseparate acts in FIG. 6B.

In some embodiments, representative process 600B may then optionallyproceed to act 640, wherein the multiplexing switch apparatus may beused to charge the sets of cells in parallel, such as is describedabove.

According to some embodiments, any number of sets of cells, includingall the sets of cells in the battery, battery pack, or system, may bedischarged simultaneously. For example, with a battery having 4 cells,all 4 cells (or only 2 or 3) could be discharged at the same time,producing whatever discharge current is desirable for the load orapplication and possible for the cells. Additionally, in someembodiments, the number of cells or sets discharged or charged isselected based on the at least one criterion, such as discharge currentfor discharging. In certain embodiments, the sequence in which thenumber of cells or sets of cells is discharged or charged is selectedbased on the at least one criterion, such as discharge current fordischarging. In some embodiments, both the number of cells or setsdischarged or charged and the sequence of doing so is selected based onthe at least one criterion, such as discharge current for discharging.

In some embodiments, process 600B may then end or repeat as necessary.For example, process 600B may repeat through any suitable number ofcycles. According to some embodiments, for each cycle or some cycles,each cell may be discharged once before any cell is discharged twice.

FIG. 6C depicts a representative high-level process 600C for controllinga battery pack. The acts of representative process 600C are described indetail in the paragraphs that follow.

In some embodiments, representative process 600C may include act 630C,wherein switches may be controlled (e.g., by a controller such as 114described above) to discharge sets (e.g., 121, 122, 123, and/or 124) ofcells (e.g., 121A-C) in the battery pack (e.g., 210) sequentially usingan integrated switching control system. Additionally, the multiplexingswitch apparatus may be connected to two or more sets of cells of thebattery or batteries. Each set of cells may comprise one or more cells.

In some embodiments, process 600C may then end or repeat as necessary.

FIG. 6D depicts a representative high-level process 600D for controllinga battery pack. The acts of representative process 600D are described indetail in the paragraphs that follow.

In some embodiments, representative process 600D may include act 630D,wherein switches may be controlled (e.g., by a controller such as 114described above) to discharge sets (e.g., 121, 122, 123, and/or 124) ofcells (e.g., 121A-C) in the battery pack (e.g., 210) based on acriterion using an integrated switching control system. Additionally,the multiplexing switch apparatus may be connected to two or more setsof cells of the battery or batteries. Each set of cells may comprise oneor more cells. In some embodiments, the criterion may include any of thefollowing: a duration of a connection between a load and a set of cellscurrently connected to the load, a delivered discharge capacity at theconnection, and a value of a function having one or more parameters.

In some embodiments, process 600D may then end or repeat as necessary.

The inventors have recognized and appreciated that some embodimentsdescribed above may produce results showing various improvements overconventional techniques when implemented. For example, in oneimplementation, cells were made of NCMA622 cathode (BASF) with 50 μm Lifoil and 25 μm Celgard 2325 separator filled with F9 (BASF) electrolytecontaining 1% by weight of lithium bis(oxalato)borate (LiBOB), with anactive electrode area of 99.41 cm². The cells were assembled into 13batteries containing 4 cells each. The batteries were subjected to 13electrical charge-discharge cycling tests performed using someembodiments at conditions summarized in Table 5 and Table 6 below. Thecells in the batteries were kept at pressure of 12 kg/cm² andtemperature of 18° C. during cycling tests.

TABLE 5 Battery test data for 4 cells simultaneously discharged witheven current distribution. Battery Battery Cycle 5^(th) Battery BatteryLife Cycle Cell Cell Discharge Charge to 800 Discharge Discharge ChargeTest Current Current mAh Capacity Current Current # mA mA Cutoff mAh mAmA 1 800 800 29 1344 200 200 2 400 400 52 1380 100 100 3 300 300 53 141275 75

TABLE 6 Battery test data for 4 cells sequentially discharged at variousdischarge pulse durations. Battery Cycle Battery Cell Cell Level ofBattery Battery Life to 5^(th) Cycle Discharge Discharge Cell No CellCell Discharge Charge 800 Discharge Pulse Pulse Current Charge DischargeTest Current Current mAh Capacity Current Duration Duration Current atSingle # mA mA Cutoff mAh mA s s mA Pulse  4 800 800 94 1064 800 1197 0200 Full  5 800 800 131 1208 800 10 30 200 Partial  6 800 800 125 1252800 1 3 200 Partial  7 800 800 46 1260 800 0.1 0.3 200 Partial  8 400400 263 1260 400 2835 0 100 Full  9 400 400 283 1284 400 10 30 100Partial 10 400 400 217 1352 400 1 3 100 Partial 11 400 400 59 1368 4000.1 0.3 100 Partial 12 300 300 334 1304 300 3912 0 75 Full 13 300 300298 1412 300 10 30 75 Partial

Table 5 (Tests #1-#3) represents comparative examples (as performed byconventional techniques) and summarizes test results when batteries werecharged and discharged at constant currents with cells connected inparallel and with charge and discharge currents distributed evenly among4 cells. Charge cutoff voltage was 4.35 V and discharge cutoff voltagewas 3.2 V. Charge-discharge cycling stopped when battery capacityreached 800 mAh.

Table 6 (Tests #4-#13) summarizes test results when batteries werecharged to 4.35 V at constant currents with cells connected in paralleland with charge discharge currents distributed evenly among 4 cells.Discharge of these batteries was performed in a way that the battery asa whole experienced constant discharge current. However, individualcells were connected to and disconnected from the load sequentially,providing discharge current pulse only for one of four cells at a time.At the end of this pulse, the next cell was connected and the previousone was disconnected. Cells experienced discharge pulses in sequences(e.g., Cell #1, 2, 3, 4, 1, 2, 3, 4, etc.) during a certain pulse timeor until discharge voltage reached 3.2 V. Tests #4, #8, and #12 providedfull cell discharge at single pulse. Other tests provided partial celldischarge at single pulse with durations of 0.1, 1, and 10 s.Charge-discharge cycling stopped when battery capacity reached 800 mAh.

FIG. 7A, corresponding to Test #13, shows the battery voltage profile atthe beginning of the 10 second pulse discharge for the first 240seconds, and FIG. 7B shows the full discharge profile to a voltage of3.2 V. In FIG. 7A, the cell numbers affected by the 10 second 300 mApulses at repeated sequences are shown for the first 80 seconds.

Referring back to Table 5 and Table 6, the inventors have recognized andappreciated that applying whole battery discharge current to the portionof the battery cells in sequence (Table 6) has led to surprising anddramatic cycle life improvement compared with homogeneous currentdistribution among all battery cells (Table 5), as has been done inconventional techniques. This cycle life improvement may be up tosix-fold, and the inventors recognized it may be a function of dischargepulse duration as well as charge-discharge rate. FIG. 7C, whichillustrates battery cycle life as a function of pulse duration at twocharge-discharge rates (corresponding to Tests #4-#11), shows that cyclelife may be especially improved with pulse time longer than 0.1 secondsand pulse duration around 10 seconds. The inventors have recognized andappreciated that improvements to battery cycle life described herein areeven available using some embodiments at partial discharge, as FIG. 7Cshows and as would not have been expected based on experience withconventional techniques. Additionally, the full capacity of all cells,even when far from uniform, can be utilized with some embodiments.

It should be appreciated that, in some embodiments, the methodsdescribed above with reference to FIGS. 4A-6 may vary, in any ofnumerous ways. For example, in some embodiments, the steps of themethods described above may be performed in a different sequence thanthat which is described, a method may involve additional steps notdescribed above, and/or a method may not involve all of the stepsdescribed above.

It should further be appreciated from the foregoing description thatsome aspects may be implemented using a computing device. FIG. 8 depictsa general purpose computing device in system 800, in the form of acomputer 810, which may be used to implement certain aspects, such asany of the controllers described above (e.g., 114).

In computer 810, components include, but are not limited to, aprocessing unit 820, a system memory 830, and a system bus 821 thatcouples various system components including the system memory to theprocessing unit 820. The system bus 821 may be any of several types ofbus structures including a memory bus or memory controller, a peripheralbus, and a local bus using any of a variety of bus architectures. By wayof example, and not limitation, such architectures include IndustryStandard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus,Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA)local bus, and Peripheral Component Interconnect (PCI) bus also known asMezzanine bus.

Computer 810 typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby computer 810 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media includes both volatileand nonvolatile, removable and non-removable media implemented in anymethod or technology for storage of information such as computerreadable instructions, data structures, program modules or other data.Computer storage media include, but are not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other one or more media that may be used to store the desiredinformation and may be accessed by computer 810. Communication mediatypically embody computer readable instructions, data structures,program modules or other data in a modulated data signal such as acarrier wave or other transport mechanism and includes any informationdelivery media. The term “modulated data signal” means a signal that hasone or more of its characteristics set or changed in such a manner as toencode information in the signal. By way of example, and not limitation,communication media include wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Combinations of the any of the aboveshould also be included within the scope of computer readable media.

The system memory 830 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 831and random access memory (RAM) 832. A basic input/output system 833(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 810, such as during start-up, istypically stored in ROM 831. RAM 832 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 820. By way of example, and notlimitation, FIG. 8 illustrates operating system 834, applicationprograms 835, other program modules 839 and program data 837.

The computer 810 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 8 illustrates a hard disk drive 841 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 851that reads from or writes to a removable, nonvolatile magnetic disk 852,and an optical disk drive 855 that reads from or writes to a removable,nonvolatile optical disk 859 such as a CD ROM or other optical media.Other removable/non-removable, volatile/nonvolatile computer storagemedia that can be used in the exemplary computing system include, butare not limited to, magnetic tape cassettes, flash memory cards, digitalversatile disks, digital video tape, solid state RAM, solid state ROM,and the like. The hard disk drive 841 is typically connected to thesystem bus 821 through an non-removable memory interface such asinterface 840, and magnetic disk drive 851 and optical disk drive 855are typically connected to the system bus 821 by a removable memoryinterface, such as interface 850.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 8 , provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 810. In FIG. 8 , for example, hard disk drive 841 isillustrated as storing operating system 844, application programs 845,other program modules 849, and program data 847. Note that thesecomponents can either be the same as or different from operating system834, application programs 835, other program modules 539, and programdata 837. Operating system 844, application programs 845, other programmodules 849, and program data 847 are given different numbers here toillustrate that, at a minimum, they are different copies. A user mayenter commands and information into the computer 810 through inputdevices such as a keyboard 892 and pointing device 891, commonlyreferred to as a mouse, trackball or touch pad. Other input devices (notshown) may include a microphone, joystick, game pad, satellite dish,scanner, or the like. These and other input devices are often connectedto the processing unit 820 through a user input interface 590 that iscoupled to the system bus, but may be connected by other interface andbus structures, such as a parallel port, game port or a universal serialbus (USB). A monitor 891 or other type of display device is alsoconnected to the system bus 821 via an interface, such as a videointerface 890. In addition to the monitor, computers may also includeother peripheral output devices such as speakers 897 and printer 899,which may be connected through a output peripheral interface 895.

The computer 810 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer880. The remote computer 880 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 810, although only a memory storage device 881 has beenillustrated in FIG. 8 . The logical connections depicted in FIG. 8include a local area network (LAN) 871 and a wide area network (WAN)873, but may also include other networks. Such networking environmentsare commonplace in offices, enterprise-wide computer networks, intranetsand the Internet.

When used in a LAN networking environment, the computer 810 is connectedto the LAN 871 through a network interface or adapter 870. When used ina WAN networking environment, the computer 810 typically includes amodem 872 or other means for establishing communications over the WAN873, such as the Internet. The modem 872, which may be internal orexternal, may be connected to the system bus 821 via the user inputinterface 890, or other appropriate mechanism. In a networkedenvironment, program modules depicted relative to the computer 810, orportions thereof, may be stored in the remote memory storage device. Byway of example, and not limitation, FIG. 8 illustrates remoteapplication programs 885 as residing on memory device 881. It will beappreciated that the network connections shown are exemplary and othermeans of establishing a communications link between the computers may beused.

Embodiments may be embodied as a computer readable storage medium (ormultiple computer readable media) (e.g., a computer memory, one or morefloppy discs, compact discs (CD), optical discs, digital video disks(DVD), magnetic tapes, flash memories, circuit configurations in FieldProgrammable Gate Arrays or other semiconductor devices, or othertangible computer storage medium) encoded with one or more programsthat, when executed on one or more computers or other processors,perform methods that implement the various embodiments discussed above.As is apparent from the foregoing examples, a computer readable storagemedium may retain information for a sufficient time to provide computerexecutable instructions in a non-transitory form. Such a computerreadable storage medium or media can be transportable, such that theprogram or programs stored thereon can be loaded onto one or moredifferent computers or other processors to implement various aspects ofthe present invention as discussed above. As used herein, the term“computer-readable storage medium” encompasses only a tangible machine,mechanism or device from which a computer may read information.Alternatively or additionally, some embodiments may be embodied as acomputer readable medium other than a computer-readable storage medium.Examples of computer readable media that are not computer readablestorage media include transitory media, like propagating signals.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention may include each individual feature, system, article,material, and/or method described herein. In addition, any combinationof two or more such features, systems, articles, materials, and/ormethods, if such features, systems, articles, materials, and/or methodsare not mutually inconsistent, is included within the scope of thepresent invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

Some embodiments may be embodied as a method, of which various exampleshave been described. The acts performed as part of the methods may beordered in any suitable way. Accordingly, embodiments may be constructedin which acts are performed in an order different than illustrated,which may include different (e.g., more or less) acts than those thatare described, and/or that may involve performing some actssimultaneously, even though the acts are shown as being performedsequentially in the embodiments specifically described above.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

What is claimed is:
 1. An electrochemical cell management systemcomprising: an electrochemical cell; and at least one controllerconfigured to control the cell such that, for at least a portion of acharge cycle, the cell is charged at a charging rate that is lower thana discharging rate of at least a portion of a previous discharge cycle,wherein the discharging rate is at least 2 times higher than thecharging rate.
 2. The electrochemical cell management system of claim 1,wherein the discharging rate is 4 times higher than the charging rate.3. The electrochemical cell management system of claim 1, wherein the atleast one controller is configured to, based on at least onecharacteristic of the cell, control charging of the cell.
 4. Theelectrochemical cell management system of claim 3, wherein the at leastone controller is configured to monitor the at least one characteristicof the cell.
 5. The electrochemical cell management system of claim 1,wherein the at least one controller is configured to induce a dischargeof the cell.
 6. The electrochemical cell management system of claim 1,wherein the at least one controller is configured to induce a dischargeof the cell at an end of a discharge cycle of the cell.
 7. Theelectrochemical cell management system of claim 1, wherein the at leastone controller is configured to induce a discharge of the cell during adischarge cycle of the cell and/or at an end of a charge cycle of thecell.
 8. The electrochemical cell management system of claim 1, whereinthe at least one controller is configured to induce a discharge of thecell before and/or after a charging step of the cell.
 9. Theelectrochemical cell management system of claim 1, wherein the at leastone controller is configured to induce a discharge of the cell at afirst rate, through at least a threshold capacity of the cell,immediately before a beginning of a charging step of the cell thatcharges the cell slower than the first rate.
 10. The electrochemicalcell management system of claim 1, wherein the at least one controllercomprises at least one processor.
 11. The electrochemical cellmanagement system of claim 1, wherein the cell comprises a lithium-metalelectrode active material.
 12. An electrochemical cell controlled by theelectrochemical cell management method of claim
 1. 13. A rechargeablebattery comprising the electrochemical cell of claim
 12. 14. A vehiclecomprising the rechargeable battery of claim
 13. 15. A vehiclecomprising the electrochemical cell of claim
 12. 16. A vehiclecomprising the electrochemical cell management system of claim
 1. 17.The electrochemical cell management system of claim 1, wherein the atleast one controller is configured to control the cell such that, over aperiod of time during which at least 5% of the capacity of the cell ischarged, an average charging rate is lower than an average dischargingrate used to discharge at least 5% of the cell's capacity during theprevious discharge cycle.
 18. The electrochemical cell management systemof claim 1, wherein the at least one controller is configured to controlthe cell such that, for at least 5% of the cell's capacity, an averagecharging rate is less than 50% of an average discharging rate at whichat least 5% of the cell's capacity was discharged during a previousdischarge step.
 19. An electrochemical cell management methodcomprising: controlling an electrochemical cell such that, for at leasta portion of a charge cycle, the cell is charged at a charging rate thatis lower than a discharging rate of at least a portion of a previousdischarge cycle, wherein the discharging rate is at least 2 times higherthan the charging rate.
 20. The electrochemical cell management methodof any claim 19, wherein the method comprises, based on at least onecharacteristic of the cell, controlling charging of the cell.
 21. Theelectrochemical cell management method of claim 20, wherein the methodcomprises monitoring the at least one characteristic of the cell. 22.The electrochemical cell management method of claim 19, wherein themethod comprises inducing a discharge of the cell.
 23. Theelectrochemical cell management method of claim 19, wherein the methodcomprises inducing a discharge of the cell at an end of a dischargecycle of the cell.
 24. The electrochemical cell management method ofclaim 19, wherein the method comprises inducing a discharge of the cellbefore and/or after a charging step of the cell.
 25. The electrochemicalcell management method of claim 19, wherein the cell comprises alithium-metal electrode active material.
 26. The electrochemical cellmanagement method of claim 19, wherein the cell is charged such that,over a period of time during which at least 5% of the capacity of thecell is charged, an average charging rate is lower than an averagedischarging rate used to discharge at least 5% of the cell's capacityduring the previous discharge cycle.
 27. The electrochemical cellmanagement method of claim 19, wherein the cell is charged such that,for at least 5% of the cell's capacity, an average charging rate is lessthan 50% of an average discharging rate at which at least 5% of thecell's capacity was discharged during a previous discharge step.